diff --git a/pkgs/applications/audio/cdparanoia/default.nix b/pkgs/applications/audio/cdparanoia/default.nix
index dd0dc8b78712675..d4d302f07d21a80 100644
--- a/pkgs/applications/audio/cdparanoia/default.nix
+++ b/pkgs/applications/audio/cdparanoia/default.nix
@@ -17,7 +17,7 @@ stdenv.mkDerivation rec {
       url = "https://trac.macports.org/export/70964/trunk/dports/audio/cdparanoia/files/patch-paranoia_paranoia.c.10.4.diff";
       sha256 = "17l2qhn8sh4jy6ryy5si6ll6dndcm0r537rlmk4a6a8vkn852vad";
     })
-  ] ++ stdenv.lib.optional stdenv.isMusl ./utils.patch;
+  ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl ./utils.patch;
 
   buildInputs = stdenv.lib.optional stdenv.isAarch64 autoreconfHook;
 
diff --git a/pkgs/applications/misc/xterm/default.nix b/pkgs/applications/misc/xterm/default.nix
index ef4092bd8034556..d807e8eb9ed50ab 100644
--- a/pkgs/applications/misc/xterm/default.nix
+++ b/pkgs/applications/misc/xterm/default.nix
@@ -20,7 +20,7 @@ stdenv.mkDerivation rec {
 
   patches = [
     ./sixel-256.support.patch
-  ] ++ stdenv.lib.optional stdenv.isMusl
+  ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl
     (fetchpatch {
       name = "posix-ptys.patch";
       url = "https://git.alpinelinux.org/cgit/aports/plain/community/xterm/posix-ptys.patch?id=3aa532e77875fa1db18c7fcb938b16647031bcc1";
diff --git a/pkgs/applications/networking/sniffers/wireshark/default.nix b/pkgs/applications/networking/sniffers/wireshark/default.nix
index 749d7449d71d313..84e10fb18bcac1d 100644
--- a/pkgs/applications/networking/sniffers/wireshark/default.nix
+++ b/pkgs/applications/networking/sniffers/wireshark/default.nix
@@ -42,7 +42,7 @@ in stdenv.mkDerivation {
 
   patches = [ ./wireshark-lookup-dumpcap-in-path.patch ]
     # https://code.wireshark.org/review/#/c/23728/
-    ++ stdenv.lib.optional stdenv.isMusl (fetchpatch {
+    ++ stdenv.lib.optional stdenv.hostPlatform.isMusl (fetchpatch {
       name = "fix-timeout.patch";
       url = "https://code.wireshark.org/review/gitweb?p=wireshark.git;a=commitdiff_plain;h=8b5b843fcbc3e03e0fc45f3caf8cf5fc477e8613;hp=94af9724d140fd132896b650d10c4d060788e4f0";
       sha256 = "1g2dm7lwsnanwp68b9xr9swspx7hfj4v3z44sz3yrfmynygk8zlv";
diff --git a/pkgs/applications/version-management/git-and-tools/git/default.nix b/pkgs/applications/version-management/git-and-tools/git/default.nix
index 4ee3d3dcf738d13..afb3716f04ce1f1 100644
--- a/pkgs/applications/version-management/git-and-tools/git/default.nix
+++ b/pkgs/applications/version-management/git-and-tools/git/default.nix
@@ -60,7 +60,7 @@ stdenv.mkDerivation {
       + (if stdenv.isDarwin then " NO_APPLE_COMMON_CRYPTO=1" else " sysconfdir=/etc/ ")
       # XXX: USE_PCRE2 might be useful in general, look into it
       # XXX other alpine options?
-      + (if stdenv.isMusl then "NO_SYS_POLL_H=1 NO_GETTEXT=YesPlease" else "");
+      + (if stdenv.hostPlatform.isMusl then "NO_SYS_POLL_H=1 NO_GETTEXT=YesPlease" else "");
 
   # build git-credential-osxkeychain if darwin
   postBuild = stdenv.lib.optionalString stdenv.isDarwin ''
diff --git a/pkgs/development/compilers/gcc/5/default.nix b/pkgs/development/compilers/gcc/5/default.nix
index 5b724b2db78f53c..eb4aff92f692139 100644
--- a/pkgs/development/compilers/gcc/5/default.nix
+++ b/pkgs/development/compilers/gcc/5/default.nix
@@ -75,7 +75,7 @@ let version = "5.5.0";
       # This could be applied unconditionally but I don't want to cause a full
       # Linux rebuild.
       ++ optional stdenv.cc.isClang ./libcxx38-and-above.patch
-      ++ optional stdenv.isMusl (fetchpatch {
+      ++ optional stdenv.hostPlatform.isMusl (fetchpatch {
         url = "https://raw.githubusercontent.com/richfelker/musl-cross-make/master/patches/gcc-5.3.0/0001-musl.diff";
         sha256 = "0pppbf8myi2kjhm3z3479ihn1cm60kycfv60gj8yy1bs0pl1qcfm";
       });
diff --git a/pkgs/development/compilers/gcc/7/default.nix b/pkgs/development/compilers/gcc/7/default.nix
index 328cca37266249f..a615b62f6bba39c 100644
--- a/pkgs/development/compilers/gcc/7/default.nix
+++ b/pkgs/development/compilers/gcc/7/default.nix
@@ -269,7 +269,7 @@ stdenv.mkDerivation ({
                  -e 's|define[[:blank:]]*MUSL_DYNAMIC_LINKER\([0-9]*\)[[:blank:]]"\([^\"]\+\)"$|define MUSL_DYNAMIC_LINKER\1 "${libc.out}\2"|g'
            done
         ''
-        + stdenv.lib.optionalString stdenv.isMusl
+        + stdenv.lib.optionalString stdenv.hostPlatform.isMusl
         ''
             sed -i gcc/config/linux.h -e '1i#undef LOCAL_INCLUDE_DIR'
         ''
diff --git a/pkgs/development/compilers/go/1.8.nix b/pkgs/development/compilers/go/1.8.nix
index 0538d93c06bb4fb..93b4ffa0eb570a0 100644
--- a/pkgs/development/compilers/go/1.8.nix
+++ b/pkgs/development/compilers/go/1.8.nix
@@ -38,7 +38,7 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ perl which pkgconfig patch makeWrapper ]
     ++ optionals stdenv.isLinux [ procps ];
   buildInputs = [ cacert pcre ]
-    ++ optionals stdenv.isGlibc [ stdenv.glibc.out stdenv.glibc.static ];
+    ++ optionals stdenv.hostPlatform.isGlibc [ stdenv.glibc.out stdenv.glibc.static ];
   propagatedBuildInputs = optionals stdenv.isDarwin [ Security Foundation ];
 
   hardeningDisable = [ "all" ];
diff --git a/pkgs/development/compilers/go/1.9.nix b/pkgs/development/compilers/go/1.9.nix
index d2e3b6253fd8e50..a123a8c00cf9785 100644
--- a/pkgs/development/compilers/go/1.9.nix
+++ b/pkgs/development/compilers/go/1.9.nix
@@ -39,7 +39,7 @@ stdenv.mkDerivation rec {
     ++ optionals stdenv.isLinux [ procps ];
   buildInputs = [ cacert pcre ]
     ++ optionals stdenv.isLinux [ stdenv.cc.libc.out ]
-    ++ optionals stdenv.isGlibc [ stdenv.glibc.static ];
+    ++ optionals stdenv.hostPlatform.isGlibc [ stdenv.glibc.static ];
   propagatedBuildInputs = optionals stdenv.isDarwin [ Security Foundation ];
 
   hardeningDisable = [ "all" ];
diff --git a/pkgs/development/compilers/llvm/4/clang/default.nix b/pkgs/development/compilers/llvm/4/clang/default.nix
index 8b066147ac65075..7cbbda8b2dd69d0 100644
--- a/pkgs/development/compilers/llvm/4/clang/default.nix
+++ b/pkgs/development/compilers/llvm/4/clang/default.nix
@@ -44,7 +44,7 @@ let
 
       # Patch for standalone doc building
       sed -i '1s,^,find_package(Sphinx REQUIRED)\n,' docs/CMakeLists.txt
-    '' + stdenv.lib.optionalString stdenv.isMusl ''
+    '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
       sed -i -e 's/lgcc_s/lgcc_eh/' lib/Driver/Tools.cpp
     '';
 
diff --git a/pkgs/development/compilers/llvm/4/default.nix b/pkgs/development/compilers/llvm/4/default.nix
index d133f2d929e72ae..9b55be842193612 100644
--- a/pkgs/development/compilers/llvm/4/default.nix
+++ b/pkgs/development/compilers/llvm/4/default.nix
@@ -18,7 +18,7 @@ let
   clang-tools-extra_src = fetch "clang-tools-extra" "1dhmp7ccfpr42bmvk3kp37ngjpf3a9m5d4kkpsn7d00hzi7fdl9m";
 
   # Add man output without introducing extra dependencies.
-  buildManPages = stdenv.buildPlatform == stdenv.hostPlatform && !stdenv.isMusl;
+  buildManPages = stdenv.buildPlatform == stdenv.hostPlatform && !stdenv.hostPlatform.isMusl;
   overrideManOutput = drv:
     if (!buildManPages) then drv else
     let drv-manpages = drv.override { enableManpages = true; }; in
diff --git a/pkgs/development/compilers/llvm/4/libc++/default.nix b/pkgs/development/compilers/llvm/4/libc++/default.nix
index 2c6759cbbf0b9a2..107704a7a52da73 100644
--- a/pkgs/development/compilers/llvm/4/libc++/default.nix
+++ b/pkgs/development/compilers/llvm/4/libc++/default.nix
@@ -15,7 +15,7 @@ stdenv.mkDerivation rec {
     ./pthread_mach_thread_np.patch
     # glibc 2.26 fix
     ./xlocale-glibc-2.26.patch
-  ] ++ stdenv.lib.optionals stdenv.isMusl [
+  ] ++ stdenv.lib.optionals stdenv.hostPlatform.isMusl [
     ./libcxx-0001-musl-hacks.patch
     ./max_align_t.patch
   ];
@@ -27,10 +27,10 @@ stdenv.mkDerivation rec {
   preConfigure = ''
     # Get headers from the cxxabi source so we can see private headers not installed by the cxxabi package
     cmakeFlagsArray=($cmakeFlagsArray -DLIBCXX_CXX_ABI_INCLUDE_PATHS="$LIBCXXABI_INCLUDE_DIR")
-  '' + lib.optionalString stdenv.isMusl ''
+  '' + lib.optionalString stdenv.hostPlatform.isMusl ''
     patchShebangs utils/cat_files.py
   '';
-  nativeBuildInputs = [ cmake ] ++ stdenv.lib.optional stdenv.isMusl python;
+  nativeBuildInputs = [ cmake ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl python;
 
   buildInputs = [ libcxxabi ] ++ lib.optional stdenv.isDarwin fixDarwinDylibNames;
 
@@ -38,7 +38,7 @@ stdenv.mkDerivation rec {
     "-DLIBCXX_LIBCXXABI_LIB_PATH=${libcxxabi}/lib"
     "-DLIBCXX_LIBCPPABI_VERSION=2"
     "-DLIBCXX_CXX_ABI=libcxxabi"
-  ] ++ stdenv.lib.optional stdenv.isMusl "-DLIBCXX_HAS_MUSL_LIBC=1";
+  ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl "-DLIBCXX_HAS_MUSL_LIBC=1";
 
   enableParallelBuilding = true;
 
diff --git a/pkgs/development/compilers/llvm/4/libc++abi.nix b/pkgs/development/compilers/llvm/4/libc++abi.nix
index db32eebdd68d6da..d37d0a070b31d4c 100644
--- a/pkgs/development/compilers/llvm/4/libc++abi.nix
+++ b/pkgs/development/compilers/llvm/4/libc++abi.nix
@@ -14,7 +14,7 @@ stdenv.mkDerivation {
     export cmakeFlags="-DLLVM_PATH=$PWD/$(ls -d llvm-*) -DLIBCXXABI_LIBCXX_PATH=$PWD/$(ls -d libcxx-*)"
   '' + stdenv.lib.optionalString stdenv.isDarwin ''
     export TRIPLE=x86_64-apple-darwin
-  '' + stdenv.lib.optionalString stdenv.isMusl ''
+  '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     patch -p1 -d $(ls -d libcxx-*) -i ${./libc++/libcxx-0001-musl-hacks.patch}
     patch -p1 -d $(ls -d libcxx-*) -i ${./libc++/max_align_t.patch}
   '';
diff --git a/pkgs/development/compilers/llvm/4/llvm.nix b/pkgs/development/compilers/llvm/4/llvm.nix
index f17d00100916df8..652e0d0104322ea 100644
--- a/pkgs/development/compilers/llvm/4/llvm.nix
+++ b/pkgs/development/compilers/llvm/4/llvm.nix
@@ -94,7 +94,7 @@ in stdenv.mkDerivation (rec {
     )
   '' + stdenv.lib.optionalString stdenv.isAarch64 ''
     patch -p0 < ${../aarch64.patch}
-  '' + stdenv.lib.optionalString stdenv.isMusl ''
+  '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     patch -p1 -i ${../TLI-musl.patch}
     patch -p1 -i ${./dynamiclibrary-musl.patch}
   '' + ''
@@ -146,7 +146,7 @@ in stdenv.mkDerivation (rec {
     "-DLLVM_TARGET_ARCH=${llvmArch}"
     #"-DLLVM_TARGETS_TO_BUILD=${llvmArch}"
   ]
-  ++ stdenv.lib.optionals stdenv.isMusl [
+  ++ stdenv.lib.optionals stdenv.hostPlatform.isMusl [
     "-DCOMPILER_RT_BUILD_SANITIZERS=OFF"
     "-DCOMPILER_RT_BUILD_XRAY=OFF"
   ];
diff --git a/pkgs/development/compilers/llvm/5/clang/default.nix b/pkgs/development/compilers/llvm/5/clang/default.nix
index 7634a8475f3b008..c1b80448b370865 100644
--- a/pkgs/development/compilers/llvm/5/clang/default.nix
+++ b/pkgs/development/compilers/llvm/5/clang/default.nix
@@ -47,7 +47,7 @@ let
 
       # Patch for standalone doc building
       sed -i '1s,^,find_package(Sphinx REQUIRED)\n,' docs/CMakeLists.txt
-    '' + stdenv.lib.optionalString stdenv.isMusl ''
+    '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
       sed -i -e 's/lgcc_s/lgcc_eh/' lib/Driver/ToolChains/*.cpp
     '';
 
diff --git a/pkgs/development/compilers/llvm/5/default.nix b/pkgs/development/compilers/llvm/5/default.nix
index 820db76bd185162..30962061bb7e199 100644
--- a/pkgs/development/compilers/llvm/5/default.nix
+++ b/pkgs/development/compilers/llvm/5/default.nix
@@ -18,7 +18,7 @@ let
   clang-tools-extra_src = fetch "clang-tools-extra" "09fjii7w43kvxvsxxs6gig9vz95vnvx1779rqd36h8kksvws3bcs";
 
   # Add man output without introducing extra dependencies.
-  buildManPages = stdenv.buildPlatform == stdenv.hostPlatform && !stdenv.isMusl;
+  buildManPages = stdenv.buildPlatform == stdenv.hostPlatform && !stdenv.hostPlatform.isMusl;
   overrideManOutput = drv:
     if (!buildManPages) then drv else
     let drv-manpages = drv.override { enableManpages = true; }; in
diff --git a/pkgs/development/compilers/llvm/5/libc++/default.nix b/pkgs/development/compilers/llvm/5/libc++/default.nix
index 7beaac5814c0b54..58f366a02e9c01e 100644
--- a/pkgs/development/compilers/llvm/5/libc++/default.nix
+++ b/pkgs/development/compilers/llvm/5/libc++/default.nix
@@ -9,7 +9,7 @@ stdenv.mkDerivation rec {
     unpackFile ${libcxxabi.src}
     export LIBCXXABI_INCLUDE_DIR="$PWD/$(ls -d libcxxabi-${version}*)/include"
   '';
-  patches = stdenv.lib.optionals stdenv.isMusl [
+  patches = stdenv.lib.optionals stdenv.hostPlatform.isMusl [
     ./libcxx-0001-musl-hacks.patch
   ];
   prePatch = ''
@@ -19,10 +19,10 @@ stdenv.mkDerivation rec {
   preConfigure = ''
     # Get headers from the cxxabi source so we can see private headers not installed by the cxxabi package
     cmakeFlagsArray=($cmakeFlagsArray -DLIBCXX_CXX_ABI_INCLUDE_PATHS="$LIBCXXABI_INCLUDE_DIR")
-  '' + lib.optionalString stdenv.isMusl ''
+  '' + lib.optionalString stdenv.hostPlatform.isMusl ''
     patchShebangs utils/cat_files.py
   '';
-  nativeBuildInputs = [ cmake ] ++ stdenv.lib.optional stdenv.isMusl python;
+  nativeBuildInputs = [ cmake ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl python;
 
   buildInputs = [ libcxxabi ] ++ lib.optional stdenv.isDarwin fixDarwinDylibNames;
 
@@ -30,7 +30,7 @@ stdenv.mkDerivation rec {
     "-DLIBCXX_LIBCXXABI_LIB_PATH=${libcxxabi}/lib"
     "-DLIBCXX_LIBCPPABI_VERSION=2"
     "-DLIBCXX_CXX_ABI=libcxxabi"
-  ] ++ stdenv.lib.optional stdenv.isMusl "-DLIBCXX_HAS_MUSL_LIBC=1";
+  ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl "-DLIBCXX_HAS_MUSL_LIBC=1";
 
   enableParallelBuilding = true;
 
diff --git a/pkgs/development/compilers/llvm/5/libc++abi.nix b/pkgs/development/compilers/llvm/5/libc++abi.nix
index 12579403ec42afb..c0d183e0422bafb 100644
--- a/pkgs/development/compilers/llvm/5/libc++abi.nix
+++ b/pkgs/development/compilers/llvm/5/libc++abi.nix
@@ -14,7 +14,7 @@ stdenv.mkDerivation {
     export cmakeFlags="-DLLVM_PATH=$PWD/$(ls -d llvm-*) -DLIBCXXABI_LIBCXX_PATH=$PWD/$(ls -d libcxx-*)"
   '' + stdenv.lib.optionalString stdenv.isDarwin ''
     export TRIPLE=x86_64-apple-darwin
-  '' + stdenv.lib.optionalString stdenv.isMusl ''
+  '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     patch -p1 -d $(ls -d libcxx-*) -i ${./libc++/libcxx-0001-musl-hacks.patch}
   '';
 
diff --git a/pkgs/development/compilers/llvm/5/llvm.nix b/pkgs/development/compilers/llvm/5/llvm.nix
index 9284f247cb1f7ab..bca199e15d7110f 100644
--- a/pkgs/development/compilers/llvm/5/llvm.nix
+++ b/pkgs/development/compilers/llvm/5/llvm.nix
@@ -88,7 +88,7 @@ in stdenv.mkDerivation (rec {
     patch -p1 -i ${./compiler-rt-codesign.patch} -d projects/compiler-rt
   '' + stdenv.lib.optionalString stdenv.isAarch64 ''
     patch -p0 < ${../aarch64.patch}
-  '' + stdenv.lib.optionalString stdenv.isMusl ''
+  '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     patch -p1 -i ${../TLI-musl.patch}
     substituteInPlace unittests/Support/CMakeLists.txt \
       --replace "add_subdirectory(DynamicLibrary)" ""
@@ -142,7 +142,7 @@ in stdenv.mkDerivation (rec {
     "-DLLVM_TARGET_ARCH=${llvmArch}"
     #"-DLLVM_TARGETS_TO_BUILD=${llvmArch}"
   ]
-  ++ stdenv.lib.optionals stdenv.isMusl [
+  ++ stdenv.lib.optionals stdenv.hostPlatform.isMusl [
     "-DCOMPILER_RT_BUILD_SANITIZERS=OFF"
     "-DCOMPILER_RT_BUILD_XRAY=OFF"
   ];
diff --git a/pkgs/development/libraries/attr/default.nix b/pkgs/development/libraries/attr/default.nix
index c1b054c643af1d0..8ac5b3c6fb7a68f 100644
--- a/pkgs/development/libraries/attr/default.nix
+++ b/pkgs/development/libraries/attr/default.nix
@@ -16,7 +16,7 @@ stdenv.mkDerivation rec {
 
   installTargets = "install install-lib install-dev";
 
-  patches = if stdenv.isMusl then [ ./fix-headers-musl.patch ] else null;
+  patches = if stdenv.hostPlatform.isMusl then [ ./fix-headers-musl.patch ] else null;
 
   meta = {
     homepage = http://savannah.nongnu.org/projects/attr/;
diff --git a/pkgs/development/libraries/boehm-gc/default.nix b/pkgs/development/libraries/boehm-gc/default.nix
index 44d63e274fc46ce..d730bd82cb22331 100644
--- a/pkgs/development/libraries/boehm-gc/default.nix
+++ b/pkgs/development/libraries/boehm-gc/default.nix
@@ -20,7 +20,7 @@ stdenv.mkDerivation rec {
   outputs = [ "out" "dev" "doc" ];
   separateDebugInfo = stdenv.isLinux;
 
-  preConfigure = stdenv.lib.optionalString stdenv.isMusl ''
+  preConfigure = stdenv.lib.optionalString hostPlatform.isMusl ''
     export NIX_CFLAGS_COMPILE+="-D_GNU_SOURCE -DUSE_MMAP -DHAVE_DL_ITERATE_PHDR"
   '';
 
@@ -32,7 +32,7 @@ stdenv.mkDerivation rec {
   configureFlags =
     [ "--enable-cplusplus" ]
     ++ lib.optional enableLargeConfig "--enable-large-config"
-    ++ lib.optional stdenv.isMusl "--disable-static";
+    ++ lib.optional hostPlatform.isMusl "--disable-static";
 
   doCheck = true; # not cross;
 
diff --git a/pkgs/development/libraries/fftw/default.nix b/pkgs/development/libraries/fftw/default.nix
index eac4542a70b6530..701209971074d0d 100644
--- a/pkgs/development/libraries/fftw/default.nix
+++ b/pkgs/development/libraries/fftw/default.nix
@@ -29,7 +29,7 @@ stdenv.mkDerivation rec {
     # all x86_64 have sse2
     # however, not all float sizes fit
     ++ optional (stdenv.isx86_64 && (precision == "single" || precision == "double") )  "--enable-sse2"
-    ++ optional (stdenv.cc.isGNU && !stdenv.isMusl) "--enable-openmp"
+    ++ optional (stdenv.cc.isGNU && !stdenv.hostPlatform.isMusl) "--enable-openmp"
     # doc generation causes Fortran wrapper generation which hard-codes gcc
     ++ optional (!withDoc) "--disable-doc";
 
diff --git a/pkgs/development/libraries/gamin/default.nix b/pkgs/development/libraries/gamin/default.nix
index e50f3baade3a3ba..2dd32b6f110001f 100644
--- a/pkgs/development/libraries/gamin/default.nix
+++ b/pkgs/development/libraries/gamin/default.nix
@@ -19,7 +19,7 @@ stdenv.mkDerivation (rec {
   patches = [ ./deadlock.patch ]
     ++ map fetchurl (import ./debian-patches.nix)
     ++ stdenv.lib.optional stdenv.cc.isClang ./returnval.patch
-    ++ stdenv.lib.optional stdenv.isMusl (fetchpatch {
+    ++ stdenv.lib.optional stdenv.hostPlatform.isMusl (fetchpatch {
       name = "fix-pthread-mutex.patch";
       url = "https://git.alpinelinux.org/cgit/aports/plain/main/gamin/fix-pthread-mutex.patch?h=3.4-stable&id=a1a836b089573752c1b0da7d144c0948b04e8ea8";
       sha256 = "13igdbqsxb3sz0h417k6ifmq2n4siwqspj6slhc7fdl5wd1fxmdz";
diff --git a/pkgs/development/libraries/icu/base.nix b/pkgs/development/libraries/icu/base.nix
index 98df2bd088738d7..81e863f0eb03a37 100644
--- a/pkgs/development/libraries/icu/base.nix
+++ b/pkgs/development/libraries/icu/base.nix
@@ -26,7 +26,7 @@ stdenv.mkDerivation {
   '';
 
   # https://sourceware.org/glibc/wiki/Release/2.26#Removal_of_.27xlocale.h.27
-  postPatch = if stdenv.isGlibc || stdenv.isMusl
+  postPatch = if stdenv.hostPlatform.isGlibc || stdenv.hostPlatform.isMusl
     then "substituteInPlace i18n/digitlst.cpp --replace '<xlocale.h>' '<locale.h>'"
     else null; # won't find locale_t on darwin
 
diff --git a/pkgs/development/libraries/libdaemon/default.nix b/pkgs/development/libraries/libdaemon/default.nix
index 7159a90d58d077d..59e576fd39231e8 100644
--- a/pkgs/development/libraries/libdaemon/default.nix
+++ b/pkgs/development/libraries/libdaemon/default.nix
@@ -24,7 +24,7 @@ stdenv.mkDerivation (rec {
     platforms = stdenv.lib.platforms.unix;
     maintainers = [ ];
   };
-} // stdenv.lib.optionalAttrs stdenv.isMusl {
+} // stdenv.lib.optionalAttrs stdenv.hostPlatform.isMusl {
   # This patch should be applied unconditionally, but doing so will cause mass rebuild.
   patches = ./fix-includes.patch;
 })
diff --git a/pkgs/development/libraries/libffi/default.nix b/pkgs/development/libraries/libffi/default.nix
index c50e8b482d47657..1339be451c294e5 100644
--- a/pkgs/development/libraries/libffi/default.nix
+++ b/pkgs/development/libraries/libffi/default.nix
@@ -15,7 +15,7 @@ stdenv.mkDerivation rec {
       url = https://src.fedoraproject.org/rpms/libffi/raw/ccffc1700abfadb0969495a6e51b964117fc03f6/f/libffi-aarch64-rhbz1174037.patch;
       sha256 = "1vpirrgny43hp0885rswgv3xski8hg7791vskpbg3wdjdpb20wbc";
     })
-    ++ stdenv.lib.optional stdenv.isMusl (fetchpatch {
+    ++ stdenv.lib.optional hostPlatform.isMusl (fetchpatch {
       name = "gnu-linux-define.patch";
       url = "https://git.alpinelinux.org/cgit/aports/plain/main/libffi/gnu-linux-define.patch?id=bb024fd8ec6f27a76d88396c9f7c5c4b5800d580";
       sha256 = "11pvy3xkhyvnjfyy293v51f1xjy3x0azrahv1nw9y9mw8bifa2j2";
diff --git a/pkgs/development/libraries/libgpg-error/default.nix b/pkgs/development/libraries/libgpg-error/default.nix
index 85069a666bc1c33..e6cb62330c4e73b 100644
--- a/pkgs/development/libraries/libgpg-error/default.nix
+++ b/pkgs/development/libraries/libgpg-error/default.nix
@@ -11,7 +11,7 @@ stdenv.mkDerivation rec {
 
   postPatch = ''
     sed '/BUILD_TIMESTAMP=/s/=.*/=1970-01-01T00:01+0000/' -i ./configure
-  '' + stdenv.lib.optionalString stdenv.isMusl ''
+  '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     ln -s lock-obj-pub.x86_64-pc-linux-musl.h src/syscfg/lock-obj-pub.linux-musl.h
   '';
 
diff --git a/pkgs/development/libraries/libidn/default.nix b/pkgs/development/libraries/libidn/default.nix
index 39faac6abbe12e5..147d6bac2f993d8 100644
--- a/pkgs/development/libraries/libidn/default.nix
+++ b/pkgs/development/libraries/libidn/default.nix
@@ -10,7 +10,7 @@ stdenv.mkDerivation rec {
 
   outputs = [ "bin" "dev" "out" "info" "devdoc" ];
 
-  doCheck = !stdenv.isDarwin && !stdenv.isMusl;
+  doCheck = !stdenv.isDarwin && !stdenv.hostPlatform.isMusl;
 
   hardeningDisable = [ "format" ];
 
diff --git a/pkgs/development/libraries/libmemcached/default.nix b/pkgs/development/libraries/libmemcached/default.nix
index b5d2015af1f2ce4..6d895290e2c23d2 100644
--- a/pkgs/development/libraries/libmemcached/default.nix
+++ b/pkgs/development/libraries/libmemcached/default.nix
@@ -18,7 +18,7 @@ stdenv.mkDerivation rec {
       url = "https://raw.githubusercontent.com/Homebrew/homebrew/bfd4a0a4626b61c2511fdf573bcbbc6bbe86340e/Library/Formula/libmemcached.rb";
       sha256 = "1gjf3vd7hiyzxjvlg2zfc3y2j0lyr6nhbws4xb5dmin3csyp8qb8";
     })
-    ++ stdenv.lib.optional stdenv.isMusl ./musl-fixes.patch;
+    ++ stdenv.lib.optional stdenv.hostPlatform.isMusl ./musl-fixes.patch;
 
   buildInputs = [ libevent ];
   propagatedBuildInputs = [ cyrus_sasl ];
diff --git a/pkgs/development/libraries/libnsl/default.nix b/pkgs/development/libraries/libnsl/default.nix
index 91baeef51b06355..9e8a46b2e6b3138 100644
--- a/pkgs/development/libraries/libnsl/default.nix
+++ b/pkgs/development/libraries/libnsl/default.nix
@@ -14,7 +14,7 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ autoreconfHook pkgconfig ];
   buildInputs = [ libtirpc ];
 
-  patches = stdenv.lib.optionals stdenv.isMusl [ ./cdefs.patch ./nis_h.patch ];
+  patches = stdenv.lib.optionals stdenv.hostPlatform.isMusl [ ./cdefs.patch ./nis_h.patch ];
 
   meta = with stdenv.lib; {
     description = "Client interface library for NIS(YP) and NIS+";
diff --git a/pkgs/development/libraries/libunistring/default.nix b/pkgs/development/libraries/libunistring/default.nix
index 2ca9874638b8848..8d1f5115bdf01e6 100644
--- a/pkgs/development/libraries/libunistring/default.nix
+++ b/pkgs/development/libraries/libunistring/default.nix
@@ -17,7 +17,7 @@ stdenv.mkDerivation rec {
     "--with-libiconv-prefix=${libiconv}"
   ];
 
-  doCheck = !stdenv.isMusl;
+  doCheck = !stdenv.hostPlatform.isMusl;
 
   enableParallelBuilding = true;
 
diff --git a/pkgs/development/libraries/libusb/default.nix b/pkgs/development/libraries/libusb/default.nix
index 67c5eec22d2739c..4704a1e5c331f5b 100644
--- a/pkgs/development/libraries/libusb/default.nix
+++ b/pkgs/development/libraries/libusb/default.nix
@@ -14,7 +14,7 @@ stdenv.mkDerivation {
     sha256 = "0nn5icrfm9lkhzw1xjvaks9bq3w6mjg86ggv3fn7kgi4nfvg8kj0";
   };
 
-  patches = stdenv.lib.optional stdenv.isMusl ./fix-headers.patch;
+  patches = stdenv.lib.optional stdenv.hostPlatform.isMusl ./fix-headers.patch;
 
   meta = {
     platforms = stdenv.lib.platforms.unix;
diff --git a/pkgs/development/libraries/libxml2/default.nix b/pkgs/development/libraries/libxml2/default.nix
index 5a2693239fb3271..3dd801df0b7fc0e 100644
--- a/pkgs/development/libraries/libxml2/default.nix
+++ b/pkgs/development/libraries/libxml2/default.nix
@@ -37,7 +37,7 @@ in stdenv.mkDerivation rec {
   enableParallelBuilding = true;
 
   doCheck = (stdenv.hostPlatform == stdenv.buildPlatform) &&
-            !stdenv.isDarwin && !stdenv.isMusl;
+            !stdenv.isDarwin && !stdenv.hostPlatform.isMusl;
 
   crossAttrs = lib.optionalAttrs (hostPlatform.libc == "msvcrt") {
     # creating the DLL is broken ATM
diff --git a/pkgs/development/libraries/mesa/default.nix b/pkgs/development/libraries/mesa/default.nix
index 4cd0857378f52ff..fa3336c4cea0008 100644
--- a/pkgs/development/libraries/mesa/default.nix
+++ b/pkgs/development/libraries/mesa/default.nix
@@ -92,7 +92,7 @@ stdenv.mkDerivation {
   patches = [
     ./glx_ro_text_segm.patch # fix for grsecurity/PaX
     ./symlink-drivers.patch
-  ] ++ stdenv.lib.optional stdenv.isMusl ./musl-fixes.patch;
+  ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl ./musl-fixes.patch;
 
   outputs = [ "out" "dev" "drivers" "osmesa" ];
 
diff --git a/pkgs/development/libraries/openssl/default.nix b/pkgs/development/libraries/openssl/default.nix
index e72efe4bb0cbdaa..af6a540b97c0fa2 100644
--- a/pkgs/development/libraries/openssl/default.nix
+++ b/pkgs/development/libraries/openssl/default.nix
@@ -24,7 +24,7 @@ let
       ++ optional (versionOlder version "1.0.2" && hostPlatform.isDarwin)
            ./darwin-arch.patch;
 
-  postPatch = if (versionAtLeast version "1.1.0" && stdenv.isMusl) then ''
+  postPatch = if (versionAtLeast version "1.1.0" && stdenv.hostPlatform.isMusl) then ''
     substituteInPlace crypto/async/arch/async_posix.h \
       --replace '!defined(__ANDROID__) && !defined(__OpenBSD__)' \
                 '!defined(__ANDROID__) && !defined(__OpenBSD__) && 0'
diff --git a/pkgs/development/libraries/polkit/default.nix b/pkgs/development/libraries/polkit/default.nix
index 3e5a99562b6000c..67bb2d2ee8aef76 100644
--- a/pkgs/development/libraries/polkit/default.nix
+++ b/pkgs/development/libraries/polkit/default.nix
@@ -40,7 +40,7 @@ stdenv.mkDerivation rec {
   ]
   # Could be applied uncondtionally but don't want to trigger rebuild
   # https://bugs.freedesktop.org/show_bug.cgi?id=50145
-  ++ stdenv.lib.optional stdenv.isMusl (fetchpatch {
+  ++ stdenv.lib.optional stdenv.hostPlatform.isMusl (fetchpatch {
     name = "netgroup-optional.patch";
     url = "https://bugs.freedesktop.org/attachment.cgi?id=118753";
     sha256 = "1zq51dhmqi9zi86bj9dq4i4pxlxm41k3k4a091j07bd78cjba038";
diff --git a/pkgs/development/libraries/qt-4.x/4.8/default.nix b/pkgs/development/libraries/qt-4.x/4.8/default.nix
index cd3c441f2e56f89..a9bd25ed28bc489 100644
--- a/pkgs/development/libraries/qt-4.x/4.8/default.nix
+++ b/pkgs/development/libraries/qt-4.x/4.8/default.nix
@@ -107,7 +107,7 @@ stdenv.mkDerivation rec {
         url = "https://src.fedoraproject.org/rpms/qt/raw/ecf530486e0fb7fe31bad26805cde61115562b2b/f/qt-aarch64.patch";
         sha256 = "1fbjh78nmafqmj7yk67qwjbhl3f6ylkp6x33b1dqxfw9gld8b3gl";
       })
-    ++ stdenv.lib.optionals stdenv.isMusl [
+    ++ stdenv.lib.optionals stdenv.hostPlatform.isMusl [
         ./qt-musl.patch
         ./qt-musl-iconv-no-bom.patch
         ./patch-qthread-stacksize.diff
diff --git a/pkgs/development/libraries/science/math/openblas/default.nix b/pkgs/development/libraries/science/math/openblas/default.nix
index ba9476b5e1a7ab7..65821be256eaaeb 100644
--- a/pkgs/development/libraries/science/math/openblas/default.nix
+++ b/pkgs/development/libraries/science/math/openblas/default.nix
@@ -115,10 +115,10 @@ stdenv.mkDerivation {
       "NUM_THREADS=64"
       "INTERFACE64=${if blas64 then "1" else "0"}"
       "NO_STATIC=1"
-    ] ++ stdenv.lib.optional stdenv.isMusl "NO_AFFINITY=1"
+    ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl "NO_AFFINITY=1"
     ++ mapAttrsToList (var: val: var + "=" + val) config;
 
-  patches = stdenv.lib.optional (!stdenv.isGlibc)
+  patches = stdenv.lib.optional (!stdenv.hostPlatform.isGlibc)
     # https://github.com/xianyi/OpenBLAS/pull/1247
     (fetchpatch {
       url = "https://github.com/xianyi/OpenBLAS/commit/88a35ff457f55e527e0e8a503a0dc61976c1846d.patch";
diff --git a/pkgs/development/libraries/stfl/default.nix b/pkgs/development/libraries/stfl/default.nix
index dbc280bf4647d83..a664de1b453a8f2 100644
--- a/pkgs/development/libraries/stfl/default.nix
+++ b/pkgs/development/libraries/stfl/default.nix
@@ -13,7 +13,7 @@ stdenv.mkDerivation rec {
   buildPhase = ''
     sed -i s/gcc/cc/g Makefile
     sed -i s%ncursesw/ncurses.h%ncurses.h% stfl_internals.h
-  '' + stdenv.lib.optionalString (!stdenv.isGlibc) ''
+  '' + stdenv.lib.optionalString (!stdenv.hostPlatform.isGlibc) ''
     sed -i 's/LDLIBS += -lncursesw/LDLIBS += -lncursesw -liconv/' Makefile
   '' + ( stdenv.lib.optionalString stdenv.isDarwin ''
     sed -i s/-soname/-install_name/ Makefile
diff --git a/pkgs/development/libraries/tbb/default.nix b/pkgs/development/libraries/tbb/default.nix
index 4a199e95325c41f..182fbb35d499ef9 100644
--- a/pkgs/development/libraries/tbb/default.nix
+++ b/pkgs/development/libraries/tbb/default.nix
@@ -16,7 +16,7 @@ with stdenv.lib; stdenv.mkDerivation rec {
     optional (stdver != null) "stdver=${stdver}"
   );
 
-  patches = stdenv.lib.optional stdenv.isMusl ./glibc-struct-mallinfo.patch;
+  patches = stdenv.lib.optional stdenv.hostPlatform.isMusl ./glibc-struct-mallinfo.patch;
 
   installPhase = ''
     mkdir -p $out/{lib,share/doc}
diff --git a/pkgs/development/libraries/ti-rpc/default.nix b/pkgs/development/libraries/ti-rpc/default.nix
index b8e4bb4c489f58e..d34a6dca78329de 100644
--- a/pkgs/development/libraries/ti-rpc/default.nix
+++ b/pkgs/development/libraries/ti-rpc/default.nix
@@ -8,7 +8,7 @@ stdenv.mkDerivation rec {
     sha256 = "1xchbxy0xql7yl7z4n1icj8r7dmly46i22fvm00vdjq64zlmqg3j";
   };
 
-  patches = stdenv.lib.optional stdenv.isMusl
+  patches = stdenv.lib.optional stdenv.hostPlatform.isMusl
     (fetchpatch {
       url = "https://raw.githubusercontent.com/openembedded/openembedded-core/2be873301420ec6ca2c70d899b7c49a7e2b0954d/meta/recipes-extended/libtirpc/libtirpc/0001-replace-__bzero-with-memset-API.patch";
       sha256 = "1jmbn0j2bnjp0j9z5vzz5xiwyv3kd28w5pixbqsy2lz6q8nii7cf";
diff --git a/pkgs/development/libraries/webkitgtk/2.4.nix b/pkgs/development/libraries/webkitgtk/2.4.nix
index a19f35112a3032d..18d20bf9c780c16 100644
--- a/pkgs/development/libraries/webkitgtk/2.4.nix
+++ b/pkgs/development/libraries/webkitgtk/2.4.nix
@@ -53,7 +53,7 @@ stdenv.mkDerivation rec {
     ./quartz-webcore.patch
     ./libc++.patch
     ./plugin-none.patch
-  ] ++ optionals stdenv.isMusl [
+  ] ++ optionals stdenv.hostPlatform.isMusl [
     ./fix-execinfo.patch
   ];
 
diff --git a/pkgs/development/libraries/webrtc-audio-processing/default.nix b/pkgs/development/libraries/webrtc-audio-processing/default.nix
index 839c017bf20c41c..b5a3aed91d900d9 100644
--- a/pkgs/development/libraries/webrtc-audio-processing/default.nix
+++ b/pkgs/development/libraries/webrtc-audio-processing/default.nix
@@ -12,7 +12,7 @@ stdenv.mkDerivation rec {
   # signal_processing/filter_ar_fast_q12_armv7.S:88: Error: selected processor does not support `sbfx r11,r6,#12,#16' in ARM mode
   patchPhase = stdenv.lib.optionalString stdenv.isArm ''
     substituteInPlace configure --replace 'armv7*|armv8*' 'disabled'
-  '' + stdenv.lib.optionalString stdenv.isMusl ''
+  '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     substituteInPlace webrtc/base/checks.cc --replace 'defined(__UCLIBC__)' 1
   '';
 
diff --git a/pkgs/development/python-modules/cffi/default.nix b/pkgs/development/python-modules/cffi/default.nix
index 10e3d0895a7e63f..5e186a8f2f8d927 100644
--- a/pkgs/development/python-modules/cffi/default.nix
+++ b/pkgs/development/python-modules/cffi/default.nix
@@ -32,7 +32,7 @@ if isPyPy then null else buildPythonPackage rec {
   # The tests use -Werror but with python3.6 clang detects some unreachable code.
   NIX_CFLAGS_COMPILE = stdenv.lib.optionals stdenv.cc.isClang [ "-Wno-unused-command-line-argument" "-Wno-unreachable-code" ];
 
-  doCheck = !stdenv.isMusl; # TODO: Investigate
+  doCheck = !stdenv.hostPlatform.isMusl; # TODO: Investigate
   checkPhase = ''
     py.test
   '';
diff --git a/pkgs/development/tools/misc/lsof/default.nix b/pkgs/development/tools/misc/lsof/default.nix
index 4395604b2b0e68b..224e0aba6ef72ef 100644
--- a/pkgs/development/tools/misc/lsof/default.nix
+++ b/pkgs/development/tools/misc/lsof/default.nix
@@ -30,7 +30,7 @@ stdenv.mkDerivation rec {
 
   patches = [ ./dfile.patch ];
 
-  postPatch = stdenv.lib.optionalString stdenv.isMusl ''
+  postPatch = stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     substituteInPlace dialects/linux/dlsof.h --replace "defined(__UCLIBC__)" 1
   '';
 
diff --git a/pkgs/development/tools/misc/patchelf/unstable.nix b/pkgs/development/tools/misc/patchelf/unstable.nix
index 19af2660f8c9e19..de68a4066d7dd57 100644
--- a/pkgs/development/tools/misc/patchelf/unstable.nix
+++ b/pkgs/development/tools/misc/patchelf/unstable.nix
@@ -11,7 +11,7 @@ stdenv.mkDerivation rec {
   };
 
   # Drop test that fails on musl (?)
-  postPatch = stdenv.lib.optionalString stdenv.isMusl ''
+  postPatch = stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     substituteInPlace tests/Makefile.am \
       --replace "set-rpath-library.sh" ""
   '';
diff --git a/pkgs/os-specific/linux/apparmor/default.nix b/pkgs/os-specific/linux/apparmor/default.nix
index 10cb1e3f9beb4f2..0f44cbfab1ed7fc 100644
--- a/pkgs/os-specific/linux/apparmor/default.nix
+++ b/pkgs/os-specific/linux/apparmor/default.nix
@@ -36,8 +36,8 @@ let
   '';
 
   # use 'if c then x else null' to avoid rebuilding
-  # patches = stdenv.lib.optionals stdenv.isMusl [
-  patches = if stdenv.isMusl then [
+  # patches = stdenv.lib.optionals stdenv.hostPlatform.isMusl [
+  patches = if stdenv.hostPlatform.isMusl then [
     ./0002-Provide-missing-secure_getenv-and-scandirat-function.patch
     ./0003-Added-missing-typedef-definitions-on-parser.patch
     ./0007-Do-not-build-install-vim-file-with-utils-package.patch
diff --git a/pkgs/os-specific/linux/audit/default.nix b/pkgs/os-specific/linux/audit/default.nix
index c9ea588eca16d6c..b3c1b97df3357eb 100644
--- a/pkgs/os-specific/linux/audit/default.nix
+++ b/pkgs/os-specific/linux/audit/default.nix
@@ -27,7 +27,7 @@ stdenv.mkDerivation rec {
 
   enableParallelBuilding = true;
 
-  patches = stdenv.lib.optional stdenv.isMusl [
+  patches = stdenv.lib.optional stdenv.hostPlatform.isMusl [
     #./0001-auditctl-include-headers-to-make-build-work-with-mus.patch
     ./0002-auparse-remove-use-of-rawmemchr.patch
     ./0003-all-get-rid-of-strndupa.patch
diff --git a/pkgs/os-specific/linux/iputils/default.nix b/pkgs/os-specific/linux/iputils/default.nix
index e4ce8f5cd53053d..a7fbcce317534d7 100644
--- a/pkgs/os-specific/linux/iputils/default.nix
+++ b/pkgs/os-specific/linux/iputils/default.nix
@@ -22,11 +22,11 @@ stdenv.mkDerivation rec {
   '';
 
   # Disable idn usage w/musl: https://github.com/iputils/iputils/pull/111
-  makeFlags = [ "USE_GNUTLS=no" ] ++ stdenv.lib.optional stdenv.isMusl "USE_IDN=no";
+  makeFlags = [ "USE_GNUTLS=no" ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl "USE_IDN=no";
 
   buildInputs = [
     libsysfs opensp openssl libcap docbook_sgml_dtd_31 SGMLSpm libgcrypt nettle
-  ] ++ stdenv.lib.optional (!stdenv.isMusl) libidn;
+  ] ++ stdenv.lib.optional (!stdenv.hostPlatform.isMusl) libidn;
 
   buildFlags = "man all ninfod";
 
diff --git a/pkgs/os-specific/linux/libnl/default.nix b/pkgs/os-specific/linux/libnl/default.nix
index 49ce7653f6b0654..f66df8163ff17b7 100644
--- a/pkgs/os-specific/linux/libnl/default.nix
+++ b/pkgs/os-specific/linux/libnl/default.nix
@@ -13,7 +13,7 @@ stdenv.mkDerivation {
 
   outputs = [ "bin" "dev" "out" "man" ];
 
-  patches = stdenv.lib.optional stdenv.isMusl
+  patches = stdenv.lib.optional stdenv.hostPlatform.isMusl
     (fetchpatch {
       url = "https://raw.githubusercontent.com/gentoo/musl/48d2a28710ae40877fd3e178ead1fb1bb0baa62c/dev-libs/libnl/files/libnl-3.3.0_rc1-musl.patch";
       sha256 = "0dd7xxikib201i99k2if066hh7gwf2i4ffckrjplq6lr206jn00r";
diff --git a/pkgs/os-specific/linux/lvm2/default.nix b/pkgs/os-specific/linux/lvm2/default.nix
index b155dd0bcb89cdb..bd84e121a7d69fc 100644
--- a/pkgs/os-specific/linux/lvm2/default.nix
+++ b/pkgs/os-specific/linux/lvm2/default.nix
@@ -41,7 +41,7 @@ stdenv.mkDerivation {
   enableParallelBuilding = true;
 
   #patches = [ ./purity.patch ];
-  patches = stdenv.lib.optionals stdenv.isMusl [
+  patches = stdenv.lib.optionals stdenv.hostPlatform.isMusl [
     (fetchpatch {
       name = "fix-stdio-usage.patch";
       url = "https://git.alpinelinux.org/cgit/aports/plain/main/lvm2/fix-stdio-usage.patch?h=3.7-stable&id=31bd4a8c2dc00ae79a821f6fe0ad2f23e1534f50";
diff --git a/pkgs/os-specific/linux/numactl/default.nix b/pkgs/os-specific/linux/numactl/default.nix
index a9706b21e4443c5..9928897ae4d4944 100644
--- a/pkgs/os-specific/linux/numactl/default.nix
+++ b/pkgs/os-specific/linux/numactl/default.nix
@@ -18,7 +18,7 @@ stdenv.mkDerivation rec {
       url = https://raw.githubusercontent.com/gentoo/gentoo/b64d15e731e3d6a7671f0ec6c34a20203cf2609d/sys-process/numactl/files/numactl-2.0.11-sysmacros.patch;
       sha256 = "05277kv3x12n2xlh3fgnmxclxfc384mkwb0v9pd91046khj6h843";
     })
-  ] ++ stdenv.lib.optional stdenv.isMusl (fetchpatch {
+  ] ++ stdenv.lib.optional stdenv.hostPlatform.isMusl (fetchpatch {
       url = https://git.alpinelinux.org/cgit/aports/plain/testing/numactl/musl.patch?id=0592b128c71c3e70d493bc7a13caed0d7fae91dd;
       sha256 = "080b0sygmg7104qbbh1amh3b322yyiajwi2d3d0vayffgva0720v";
     });
diff --git a/pkgs/os-specific/linux/pam/default.nix b/pkgs/os-specific/linux/pam/default.nix
index a3dd6562b836af6..a392461ad9f382a 100644
--- a/pkgs/os-specific/linux/pam/default.nix
+++ b/pkgs/os-specific/linux/pam/default.nix
@@ -9,7 +9,7 @@ stdenv.mkDerivation rec {
     sha256 = "1fyi04d5nsh8ivd0rn2y0z83ylgc0licz7kifbb6xxi2ylgfs6i4";
   };
 
-  patches = stdenv.lib.optionals stdenv.isMusl [
+  patches = stdenv.lib.optionals stdenv.hostPlatform.isMusl [
     (fetchpatch {
       url = "https://git.alpinelinux.org/cgit/aports/plain/main/linux-pam/fix-compat.patch?id=05a62bda8ec255d7049a2bd4cf0fdc4b32bdb2cc";
       sha256 = "1h5yp5h2mqp1fcwiwwklyfpa69a3i03ya32pivs60fd7g5bqa7sf";
@@ -61,7 +61,7 @@ stdenv.mkDerivation rec {
 
   preConfigure = ''
     configureFlags="$configureFlags --includedir=$out/include/security"
-  '' + stdenv.lib.optionalString stdenv.isMusl ''
+  '' + stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
       # export ac_cv_search_crypt=no
       # (taken from Alpine linux, apparently insecure but also doesn't build O:))
       # disable insecure modules
diff --git a/pkgs/os-specific/linux/shadow/default.nix b/pkgs/os-specific/linux/shadow/default.nix
index e79a43ca504bf3e..b23a529d708d3e2 100644
--- a/pkgs/os-specific/linux/shadow/default.nix
+++ b/pkgs/os-specific/linux/shadow/default.nix
@@ -9,7 +9,7 @@ let
   glibc =
     if hostPlatform != buildPlatform
     then glibcCross
-    else assert stdenv.isGlibc; stdenv.cc.libc;
+    else assert hostPlatform.isGlibc; stdenv.cc.libc;
 
   dots_in_usernames = fetchpatch {
     url = http://sources.gentoo.org/cgi-bin/viewvc.cgi/gentoo-x86/sys-apps/shadow/files/shadow-4.1.3-dots-in-usernames.patch;
diff --git a/pkgs/os-specific/linux/systemd/default.nix b/pkgs/os-specific/linux/systemd/default.nix
index 2b0a0310ac22185..8cdf5a67ea64e4d 100644
--- a/pkgs/os-specific/linux/systemd/default.nix
+++ b/pkgs/os-specific/linux/systemd/default.nix
@@ -12,8 +12,8 @@ assert stdenv.isLinux;
 # XXX
 let
   getent-bin =
-         if stdenv.isGlibc then stdenv.cc.libc.bin
-    else if stdenv.isMusl then "${musl-getent}"
+         if stdenv.hostPlatform.isGlibc then stdenv.cc.libc.bin
+    else if stdenv.hostPlatform.isMusl then "${musl-getent}"
     else throw "unsupported abi for systemd";
   getent = "${getent-bin}/bin/getent";
 
@@ -82,7 +82,7 @@ in stdenv.mkDerivation rec {
       "--with-sysvrcnd-path="
       "--with-rc-local-script-path-stop=/etc/halt.local"
     ]
-    ++ stdenv.lib.optionals stdenv.isMusl [
+    ++ stdenv.lib.optionals stdenv.hostPlatform.isMusl [
       "--disable-localed"
       "--disable-machined"
       "--disable-myhostname"
@@ -104,7 +104,7 @@ in stdenv.mkDerivation rec {
         url = "https://github.com/systemd/systemd/commit/58a78ae77063eddfcd23ea272bd2e0ddc9ea3ff7.patch";
         sha256 = "0g3pvqigs69mciw6lj3zg12dmxnhwxndwxdjg78af52xrp0djfg8";
     })
-  ] ++ stdenv.lib.optionals stdenv.isMusl (import ./musl-patches.nix { inherit fetchFromGitHub; inherit (stdenv) lib; });
+  ] ++ stdenv.lib.optionals stdenv.hostPlatform.isMusl (import ./musl-patches.nix { inherit fetchFromGitHub; inherit (stdenv) lib; });
 
   preConfigure =
     ''
diff --git a/pkgs/servers/pulseaudio/default.nix b/pkgs/servers/pulseaudio/default.nix
index 4b7d3d400daf4e5..2f102b58f141955 100644
--- a/pkgs/servers/pulseaudio/default.nix
+++ b/pkgs/servers/pulseaudio/default.nix
@@ -44,7 +44,7 @@ stdenv.mkDerivation rec {
   };
 
   patches = [ ./caps-fix.patch ]
-    ++ stdenv.lib.optional stdenv.isMusl (fetchpatch {
+    ++ stdenv.lib.optional stdenv.hostPlatform.isMusl (fetchpatch {
       name = "padsp-fix.patch";
       url = "https://git.alpinelinux.org/cgit/aports/plain/testing/pulseaudio/0001-padsp-Make-it-compile-on-musl.patch?id=167be02bf4618a90328e2b234f6a63a5dc05f244";
       sha256 = "0gf4w25zi123ghk0njapysvrlljkc3hyanacgiswfnnm1i8sab1q";
diff --git a/pkgs/servers/sql/mariadb/default.nix b/pkgs/servers/sql/mariadb/default.nix
index fcb18e93d3c2b6b..b8ee85d65e748da 100644
--- a/pkgs/servers/sql/mariadb/default.nix
+++ b/pkgs/servers/sql/mariadb/default.nix
@@ -62,7 +62,7 @@ common = rec { # attributes common to both builds
     "-DPLUGIN_AUTH_GSSAPI_CLIENT=NO"
   ]
     ++ optional stdenv.isDarwin "-DCURSES_LIBRARY=${ncurses.out}/lib/libncurses.dylib"
-    ++ optional stdenv.isMusl "-DWITHOUT_TOKUDB=1" # mariadb docs say disable this for musl
+    ++ optional stdenv.hostPlatform.isMusl "-DWITHOUT_TOKUDB=1" # mariadb docs say disable this for musl
     ;
 
   preConfigure = ''
diff --git a/pkgs/servers/squid/4.nix b/pkgs/servers/squid/4.nix
index 7bdd646d642d57b..f509db779a3cf96 100644
--- a/pkgs/servers/squid/4.nix
+++ b/pkgs/servers/squid/4.nix
@@ -29,7 +29,7 @@ stdenv.mkDerivation rec {
     "--enable-removal-policies=lru,heap"
     "--enable-delay-pools"
     "--enable-x-accelerator-vary"
-  ] ++ stdenv.lib.optional (stdenv.isLinux && !stdenv.isMusl) "--enable-linux-netfilter";
+  ] ++ stdenv.lib.optional (stdenv.isLinux && !stdenv.hostPlatform.isMusl) "--enable-linux-netfilter";
 
   meta = with stdenv.lib; {
     description = "A caching proxy for the Web supporting HTTP, HTTPS, FTP, and more";
diff --git a/pkgs/servers/squid/default.nix b/pkgs/servers/squid/default.nix
index 23c985ed3d6bcee..a6e4648ff17ff78 100644
--- a/pkgs/servers/squid/default.nix
+++ b/pkgs/servers/squid/default.nix
@@ -23,7 +23,7 @@ stdenv.mkDerivation rec {
     "--enable-removal-policies=lru,heap"
     "--enable-delay-pools"
     "--enable-x-accelerator-vary"
-  ] ++ stdenv.lib.optional (stdenv.isLinux && !stdenv.isMusl) "--enable-linux-netfilter";
+  ] ++ stdenv.lib.optional (stdenv.isLinux && !stdenv.hostPlatform.isMusl) "--enable-linux-netfilter";
 
   meta = with stdenv.lib; {
     description = "A caching proxy for the Web supporting HTTP, HTTPS, FTP, and more";
diff --git a/pkgs/servers/x11/xorg/overrides.nix b/pkgs/servers/x11/xorg/overrides.nix
index bb66decd30bf9c9..c6466598195e154 100644
--- a/pkgs/servers/x11/xorg/overrides.nix
+++ b/pkgs/servers/x11/xorg/overrides.nix
@@ -493,7 +493,7 @@ in
           args.udev
         ];
         patches = commonPatches;
-        prePatch = stdenv.lib.optionalString stdenv.isMusl ''
+        prePatch = stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
           export CFLAGS+=" -D__uid_t=uid_t -D__gid_t=gid_t"
         '';
         configureFlags = [
diff --git a/pkgs/shells/fish/default.nix b/pkgs/shells/fish/default.nix
index c07f48c6ad520e6..3078dd2dcab3293 100644
--- a/pkgs/shells/fish/default.nix
+++ b/pkgs/shells/fish/default.nix
@@ -12,8 +12,9 @@
 with stdenv.lib;
 
 let
-  getent = if stdenv.isMusl then "${musl-getent}/bin/getent"
-                            else "${glibc.bin}/bin/getent";
+  getent = if stdenv.hostPlatform.isMusl
+             then "${musl-getent}/bin/getent"
+             else "${glibc.bin}/bin/getent";
   etcConfigAppendixText = ''
     ############### ↓ Nix hook for sourcing /etc/fish/config.fish ↓ ###############
     #                                                                             #
diff --git a/pkgs/stdenv/generic/default.nix b/pkgs/stdenv/generic/default.nix
index e663a6ed0ca0b62..d5885193b9bc456 100644
--- a/pkgs/stdenv/generic/default.nix
+++ b/pkgs/stdenv/generic/default.nix
@@ -117,8 +117,7 @@ let
       # Utility flags to test the type of platform.
       inherit (hostPlatform)
         isDarwin isLinux isSunOS isHurd isCygwin isFreeBSD isOpenBSD
-        isi686 isx86_64 is64bit isArm isAarch64 isMips isBigEndian
-        isMusl isGlibc;
+        isi686 isx86_64 is64bit isArm isAarch64 isMips isBigEndian;
 
       # Whether we should run paxctl to pax-mark binaries.
       needsPax = isLinux;
diff --git a/pkgs/tools/misc/screen/default.nix b/pkgs/tools/misc/screen/default.nix
index 8fecd3fffceac5a..1753f52ab1b6c16 100644
--- a/pkgs/tools/misc/screen/default.nix
+++ b/pkgs/tools/misc/screen/default.nix
@@ -16,7 +16,7 @@ stdenv.mkDerivation rec {
     "--enable-colors256"
   ];
 
-  patches = stdenv.lib.optional stdenv.isMusl
+  patches = stdenv.lib.optional stdenv.hostPlatform.isMusl
     (fetchpatch {
       url = https://gist.githubusercontent.com/yujinakayama/4608863/raw/76b9f89af5e5a2e97d9a0f36aac989fb56cf1447/gistfile1.diff;
       sha256 = "0f9bf83p8zdxaa1pr75jyf5g8xr3r8kv7cyzzbpraa1q4j15ss1p";
diff --git a/pkgs/tools/networking/inetutils/default.nix b/pkgs/tools/networking/inetutils/default.nix
index 28e234941458809..c5ecb5eb6dade21 100644
--- a/pkgs/tools/networking/inetutils/default.nix
+++ b/pkgs/tools/networking/inetutils/default.nix
@@ -16,7 +16,7 @@ stdenv.mkDerivation rec {
   buildInputs = [ ncurses /* for `talk' */ perl /* for `whois' */ help2man ];
 
   configureFlags = [ "--with-ncurses-include-dir=${ncurses.dev}/include" ]
-  ++ stdenv.lib.optionals stdenv.isMusl [ # Musl doesn't define rcmd
+  ++ stdenv.lib.optionals stdenv.hostPlatform.isMusl [ # Musl doesn't define rcmd
     "--disable-rcp"
     "--disable-rsh"
     "--disable-rlogin"
@@ -31,7 +31,7 @@ stdenv.mkDerivation rec {
   postInstall = ''
     # XXX: These programs are normally installed setuid but since it
     # fails, they end up being non-executable, hence this hack.
-    chmod +x $out/bin/{ping,ping6,${stdenv.lib.optionalString (!stdenv.isMusl) ''rcp,rlogin,rsh,''}traceroute}
+    chmod +x $out/bin/{ping,ping6,${stdenv.lib.optionalString (!stdenv.hostPlatform.isMusl) ''rcp,rlogin,rsh,''}traceroute}
   '';
 
   meta = {
diff --git a/pkgs/tools/networking/iperf/3.nix b/pkgs/tools/networking/iperf/3.nix
index bf66803e827ce5e..b9e47ecd7f90445 100644
--- a/pkgs/tools/networking/iperf/3.nix
+++ b/pkgs/tools/networking/iperf/3.nix
@@ -10,11 +10,11 @@ stdenv.mkDerivation rec {
 
   buildInputs = [ openssl ];
 
-  preConfigure = stdenv.lib.optionalString (stdenv.isMusl) ''
+  preConfigure = stdenv.lib.optionalString stdenv.hostPlatform.isMusl ''
     NIX_CFLAGS_COMPILE+=" -D_GNU_SOURCE"
   '';
 
-  patches = stdenv.lib.optionals (stdenv.isMusl) [
+  patches = stdenv.lib.optionals stdenv.hostPlatform.isMusl [
     (fetchpatch {
       url = "http://git.alpinelinux.org/cgit/aports/plain/main/iperf3/build-fixes.patch";
       name = "fix-musl-build.patch";
diff --git a/pkgs/tools/networking/unbound/default.nix b/pkgs/tools/networking/unbound/default.nix
index c96914fd2af8f06..cc2f994d0d54dd2 100644
--- a/pkgs/tools/networking/unbound/default.nix
+++ b/pkgs/tools/networking/unbound/default.nix
@@ -27,7 +27,7 @@ stdenv.mkDerivation rec {
 
   installFlags = [ "configfile=\${out}/etc/unbound/unbound.conf" ];
 
-  preFixup = stdenv.lib.optionalString (stdenv.isLinux && !stdenv.isMusl) # XXX: revisit
+  preFixup = stdenv.lib.optionalString (stdenv.isLinux && !stdenv.hostPlatform.isMusl) # XXX: revisit
     # Build libunbound again, but only against nettle instead of openssl.
     # This avoids gnutls.out -> unbound.lib -> openssl.out.
     # There was some problem with this on Darwin; let's not complicate non-Linux.
diff --git a/pkgs/tools/system/smartmontools/default.nix b/pkgs/tools/system/smartmontools/default.nix
index a34208242f3b79c..e5b2d54e585d1c2 100644
--- a/pkgs/tools/system/smartmontools/default.nix
+++ b/pkgs/tools/system/smartmontools/default.nix
@@ -22,7 +22,7 @@ in stdenv.mkDerivation rec {
 
   patches = [ ./smartmontools.patch ]
     # https://www.smartmontools.org/changeset/4603
-    ++ stdenv.lib.optional stdenv.isMusl (fetchpatch {
+    ++ stdenv.lib.optional stdenv.hostPlatform.isMusl (fetchpatch {
       name = "musl-canonicalize_file_name.patch";
       url = "https://www.smartmontools.org/changeset/4603?format=diff&new=4603";
       sha256 = "06s9pcd95snjkrbfrsjby2lln3lnwjd21bgabmvr4p7fx19b75zp";
diff --git a/pkgs/tools/text/agrep/default.nix b/pkgs/tools/text/agrep/default.nix
index c125cdb52fc6260..10d3a47cc85eb8c 100644
--- a/pkgs/tools/text/agrep/default.nix
+++ b/pkgs/tools/text/agrep/default.nix
@@ -13,7 +13,7 @@ stdenv.mkDerivation rec {
   };
 
   # Related: https://github.com/Wikinaut/agrep/pull/11
-  prePatch = stdenv.lib.optionalString (stdenv.isMusl || stdenv.isDarwin) ''
+  prePatch = stdenv.lib.optionalString (stdenv.hostPlatform.isMusl || stdenv.isDarwin) ''
     sed -i '1i#include <sys/stat.h>' checkfil.c newmgrep.c recursiv.c
   '';
   installPhase = ''
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 20358c07e959a17..73ce185acb5003b 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -8696,7 +8696,7 @@ with pkgs;
   libcCross = assert targetPlatform != buildPlatform; libcCrossChooser targetPlatform.libc;
 
   # Only supported on Linux, using glibc
-  glibcLocales = if stdenv.isGlibc then callPackage ../development/libraries/glibc/locales.nix { } else null;
+  glibcLocales = if hostPlatform.isGlibc then callPackage ../development/libraries/glibc/locales.nix { } else null;
 
   glibcInfo = callPackage ../development/libraries/glibc/info.nix { };
 
@@ -12853,7 +12853,7 @@ with pkgs;
 
   inherit (callPackages ../os-specific/linux/kernel-headers { })
     linuxHeaders_4_4 linuxHeaders_4_15;
-  linuxHeaders = if stdenv.isMusl then linuxHeaders_4_15 else linuxHeaders_4_4;
+  linuxHeaders = if hostPlatform.isMusl then linuxHeaders_4_15 else linuxHeaders_4_4;
 
   kernelPatches = callPackage ../os-specific/linux/kernel/patches.nix { };