diff --git a/src/header/_fenv/cbindgen.toml b/src/header/_fenv/cbindgen.toml
index 6b94e4d28e..c4fef18554 100644
--- a/src/header/_fenv/cbindgen.toml
+++ b/src/header/_fenv/cbindgen.toml
@@ -1,4 +1,12 @@
-sys_includes = ["stdint.h"]
+# POSIX header spec: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/fenv.h.html
+#
+# There are no spec quotations relating to includes
+#
+# TODO figure out what type to use for `fenv_t` and `fexcept_t`
+#      currently using `c_ulonglong` as it doesn't bring in
+#      stdint.h (which would be considered namespace pollution)
+#
+# NOTE this header is not currently exported as we are using openlibm
 include_guard = "_RELIBC_FENV_H"
 language = "C"
 style = "Tag"
diff --git a/src/header/_fenv/mod.rs b/src/header/_fenv/mod.rs
index 54dd24062c..c09b2882a7 100644
--- a/src/header/_fenv/mod.rs
+++ b/src/header/_fenv/mod.rs
@@ -2,7 +2,7 @@
 //!
 //! See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/fenv.h.html>.
 
-use crate::platform::types::c_int;
+use crate::platform::types::{c_int, c_ulonglong};
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/fenv.h.html>.
 pub const FE_ALL_EXCEPT: c_int = 0;
@@ -10,12 +10,12 @@ pub const FE_ALL_EXCEPT: c_int = 0;
 pub const FE_TONEAREST: c_int = 0;
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/fenv.h.html>.
-pub type fexcept_t = u64;
+pub type fexcept_t = c_ulonglong;
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/fenv.h.html>.
 #[repr(C)]
 pub struct fenv_t {
-    pub cw: u64,
+    pub cw: c_ulonglong,
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/feclearexcept.html>.