diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index f378dda..6eb82a1 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-12, macos-13, macos-14, macos-15]
+        os: [ubuntu-latest]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Set up Homebrew
diff --git a/Formula/macaulay2.rb b/Formula/macaulay2.rb
index 2bcf82a..1b9524e 100644
--- a/Formula/macaulay2.rb
+++ b/Formula/macaulay2.rb
@@ -2,20 +2,9 @@ class Macaulay2 < Formula
   @name = "M2"
   desc "Software system for algebraic geometry research"
   homepage "http://macaulay2.com"
-  url "https://github.com/Macaulay2/M2/archive/refs/tags/release-1.24.05.tar.gz"
-  sha256 "63b8c9931a5cbd0b937ad6ddb81530c26f3fbe5971cc935d294772652ebcf101"
+  url "https://github.com/Macaulay2/M2/archive/refs/tags/release-1.19.tar.gz"
+  sha256 "08c110d0081c8408eec60e11cee363d9b62e82c212a9f099247be1940057b071"
   license any_of: ["GPL-2.0-only", "GPL-3.0-only"]
-  revision 1
-
-  head "https://github.com/Macaulay2/M2/archive/refs/heads/development.tar.gz"
-
-  bottle do
-    root_url "https://ghcr.io/v2/macaulay2/tap"
-    sha256 cellar: :any, arm64_sonoma: "9fa62984c1f40bda3720b556fb384bcec36fa7780c76d57234b039b1a6b430fd"
-    sha256 cellar: :any, ventura:      "5b821509c8a71d914fb4fb2d2887601a315293052b01e86803ea85d5e460b645"
-    sha256 cellar: :any, monterey:     "5c987cd5c60e83ad5ffe5fcb772277b2fc39918c6fcd252936630635eb455ae8"
-    sha256               x86_64_linux: "fdd8b0361c22e532c5b5107998d7dce913adaa23119ce5eca75d137cee48110d"
-  end
 
   depends_on "bison" => :build
   depends_on "cmake" => :build
@@ -32,16 +21,17 @@ class Macaulay2 < Formula
   depends_on "gdbm"
   depends_on "givaro"
   depends_on "gmp"
+  depends_on "libatomic_ops"
   depends_on "libxml2" unless OS.mac?
   depends_on "libffi"
   depends_on "mpfi"
   depends_on "mpfr"
   depends_on "mpsolve"
+  depends_on "msolve"
   depends_on "node"
   depends_on "ntl"
   depends_on "openblas" unless OS.mac?
   depends_on "readline"
-  depends_on "tbb"
 
   depends_on "cohomcalg" => :recommended
   depends_on "csdp" => :recommended
@@ -60,9 +50,6 @@ def install
     # Don't print the shims prefix path
     inreplace "M2/Macaulay2/packages/Macaulay2Doc/functions/findProgram-doc.m2", "Verbose => true", "Verbose => false"
 
-    # Don't print the shims prefix path
-    inreplace "M2/Macaulay2/packages/ForeignFunctions.m2", "get \"!brew --prefix\"", "getenv \"HOMEBREW_PREFIX\""
-
     # c.f. https://github.com/Macaulay2/M2/issues/2682
     inreplace "M2/Macaulay2/d/CMakeLists.txt", "M2-supervisor", "M2-supervisor quadmath" unless OS.mac?
 
@@ -79,8 +66,8 @@ def install
     args << "-DBUILD_NATIVE=OFF"
     args << "-DBUILD_TESTING=OFF"
     args << "-DCMAKE_PREFIX_PATH=#{lib_prefix}"
-    args << "-DTBB_ROOT_DIR=#{Formula["tbb"].prefix}"
     args << "-DWITH_OMP=ON" if build.with?("libomp") || !OS.mac?
+    args << "-DWITH_TBB=OFF"
 
     if OS.mac?
       ENV["MACOSX_DEPLOYMENT_TARGET"] = MacOS.version
@@ -99,26 +86,12 @@ def install
     system "#{bin}/M2", "--version"
     system "#{bin}/M2", "--check", "1", "-e", "exit 0"
     # system "#{bin}/M2", "--check", "2", "-e", "exit 0"
+    # system "#{bin}/M2", "--check", "3", "-e", "exit 0"
   end
 end
 
 __END__
 
-diff --git a/M2/Macaulay2/m2/packages.m2 b/M2/Macaulay2/m2/packages.m2
-index d5ddc33bc..92f700b5c 100644
---- a/M2/Macaulay2/m2/packages.m2
-+++ b/M2/Macaulay2/m2/packages.m2
-@@ -188,7 +188,6 @@ needsPackage String  := opts -> pkgname -> (
-     and instance(pkg := value PackageDictionary#pkgname, Package)
-     and (opts.FileName === null or
- 	realpath opts.FileName == realpath pkg#"source file")
--    and pkg.PackageIsLoaded
-     then use value PackageDictionary#pkgname
-     else loadPackage(pkgname, opts))
-
--- 
-2.34.3
-
 diff --git a/M2/cmake/check-libraries.cmake b/M2/cmake/check-libraries.cmake
 index ca3effff15..45e6b11c81 100644
 --- a/M2/cmake/check-libraries.cmake
@@ -134,19 +107,3 @@ def install
    set(Boost_stacktrace_lib "Boost::stacktrace_backtrace")
 -- 
 2.38.1
-
-diff --git a/M2/Macaulay2/packages/Topcom.m2 b/M2/Macaulay2/packages/Topcom.m2
-index 15832adfb1..e9af682733 100644
---- a/M2/Macaulay2/packages/Topcom.m2
-+++ b/M2/Macaulay2/packages/Topcom.m2
-@@ -317,7 +317,7 @@ topcomIsTriangulation(Matrix, List) := Boolean => opts -> (Vin, T) -> (
-       << "Index sets do not correspond to full-dimensional simplices" << endl;
-       return false;
-    );
--   (outfile, errfile) := callTopcom("points2nflips --checktriang -v", {topcomPoints(V, Homogenize=>false), [], T });
-+   (outfile, errfile) := callTopcom("points2nflips --checktriang --memopt -v", {topcomPoints(V, Homogenize=>false), [], T });
-    not match("not valid", get errfile)
- )
- 
--- 
-2.38.1