diff --git a/src/solid/aarch64.rs b/src/solid/aarch64.rs
index ceabea397b80..4032488b6c0d 100644
--- a/src/solid/aarch64.rs
+++ b/src/solid/aarch64.rs
@@ -1,4 +1,4 @@
-pub type c_char = i8;
+pub type c_char = u8;
 pub type wchar_t = u32;
 pub type c_long = i64;
 pub type c_ulong = u64;
diff --git a/src/solid/arm.rs b/src/solid/arm.rs
index 04cc1542deae..55240068aa08 100644
--- a/src/solid/arm.rs
+++ b/src/solid/arm.rs
@@ -1,4 +1,4 @@
-pub type c_char = i8;
+pub type c_char = u8;
 pub type wchar_t = u32;
 pub type c_long = i32;
 pub type c_ulong = u32;
diff --git a/src/unix/linux_like/android/b64/riscv64/mod.rs b/src/unix/linux_like/android/b64/riscv64/mod.rs
index f214fe33702a..d35c40895510 100644
--- a/src/unix/linux_like/android/b64/riscv64/mod.rs
+++ b/src/unix/linux_like/android/b64/riscv64/mod.rs
@@ -1,7 +1,7 @@
 use crate::off64_t;
 use crate::prelude::*;
 
-pub type c_char = i8;
+pub type c_char = u8;
 pub type wchar_t = u32;
 pub type greg_t = i64;
 pub type __u64 = c_ulonglong;
diff --git a/src/unix/linux_like/linux/uclibc/x86_64/mod.rs b/src/unix/linux_like/linux/uclibc/x86_64/mod.rs
index 07574581d77c..b41936f94fee 100644
--- a/src/unix/linux_like/linux/uclibc/x86_64/mod.rs
+++ b/src/unix/linux_like/linux/uclibc/x86_64/mod.rs
@@ -6,7 +6,7 @@ use crate::prelude::*;
 pub type blkcnt_t = i64;
 pub type blksize_t = i64;
 pub type clock_t = i64;
-pub type c_char = u8;
+pub type c_char = i8;
 pub type c_long = i64;
 pub type c_ulong = u64;
 pub type fsblkcnt_t = c_ulong;
diff --git a/src/unix/newlib/vita/mod.rs b/src/unix/newlib/vita/mod.rs
index 120c4d54972f..1a8c89319fa2 100644
--- a/src/unix/newlib/vita/mod.rs
+++ b/src/unix/newlib/vita/mod.rs
@@ -3,7 +3,7 @@ use crate::prelude::*;
 
 pub type clock_t = c_long;
 
-pub type c_char = i8;
+pub type c_char = u8;
 pub type wchar_t = u32;
 
 pub type c_long = i32;
diff --git a/src/unix/nuttx/mod.rs b/src/unix/nuttx/mod.rs
index 95d1156bfc48..78ecf3f13350 100644
--- a/src/unix/nuttx/mod.rs
+++ b/src/unix/nuttx/mod.rs
@@ -5,7 +5,17 @@ pub type nlink_t = u16;
 pub type ino_t = u16;
 pub type blkcnt_t = u64;
 pub type blksize_t = i16;
-pub type c_char = i8;
+cfg_if! {
+    if #[cfg(any(
+        target_arch = "arm",
+        target_arch = "riscv32",
+        target_arch = "riscv64",
+    ))] {
+        pub type c_char = u8;
+    } else {
+        pub type c_char = i8;
+    }
+}
 pub type c_long = isize;
 pub type c_ulong = usize;
 pub type cc_t = u8;
diff --git a/src/unix/redox/mod.rs b/src/unix/redox/mod.rs
index db854dd6300e..1c8bb40e746f 100644
--- a/src/unix/redox/mod.rs
+++ b/src/unix/redox/mod.rs
@@ -1,6 +1,12 @@
 use crate::prelude::*;
 
-pub type c_char = i8;
+cfg_if! {
+    if #[cfg(target_arch = "aarch64")] {
+        pub type c_char = u8;
+    } else {
+        pub type c_char = i8;
+    }
+}
 pub type wchar_t = i32;
 
 cfg_if! {
diff --git a/src/unix/solarish/mod.rs b/src/unix/solarish/mod.rs
index 9fce13226afc..83d94bff8437 100644
--- a/src/unix/solarish/mod.rs
+++ b/src/unix/solarish/mod.rs
@@ -2,7 +2,13 @@ use core::mem::size_of;
 
 use crate::prelude::*;
 
-pub type c_char = i8;
+cfg_if! {
+    if #[cfg(target_arch = "aarch64")] {
+        pub type c_char = u8;
+    } else {
+        pub type c_char = i8;
+    }
+}
 pub type c_long = i64;
 pub type c_ulong = u64;
 pub type caddr_t = *mut c_char;
diff --git a/src/vxworks/riscv32.rs b/src/vxworks/riscv32.rs
index e617bb83c6ce..40a8e338e83a 100644
--- a/src/vxworks/riscv32.rs
+++ b/src/vxworks/riscv32.rs
@@ -1,4 +1,4 @@
-pub type c_char = i8;
+pub type c_char = u8;
 pub type wchar_t = i32;
 pub type c_long = i32;
 pub type c_ulong = u32;
diff --git a/src/vxworks/riscv64.rs b/src/vxworks/riscv64.rs
index 5e95ea2567dd..ccd68b0c64f8 100644
--- a/src/vxworks/riscv64.rs
+++ b/src/vxworks/riscv64.rs
@@ -1,4 +1,4 @@
-pub type c_char = i8;
+pub type c_char = u8;
 pub type wchar_t = i32;
 pub type c_long = i64;
 pub type c_ulong = u64;