diff --git a/src/header/sys_random/cbindgen.toml b/src/header/sys_random/cbindgen.toml
index d83dd8b5eb..85ff9e5953 100644
--- a/src/header/sys_random/cbindgen.toml
+++ b/src/header/sys_random/cbindgen.toml
@@ -1,7 +1,9 @@
-sys_includes = ["sys/types.h"]
-include_guard = "_SYS_RANDOM_H"
+after_includes = """
+#include <bits/size-t.h>  // for size_t from sys/types.h
+#include <bits/ssize-t.h> // for ssize_t from sys/types.h
+"""
+include_guard = "_RELIBC_SYS_RANDOM_H"
 language = "C"
-style = "Tag"
 no_includes = true
 cpp_compat = true
 
diff --git a/src/header/sys_random/mod.rs b/src/header/sys_random/mod.rs
index 57040d469a..8393a78fd4 100644
--- a/src/header/sys_random/mod.rs
+++ b/src/header/sys_random/mod.rs
@@ -13,11 +13,19 @@ use crate::{
 };
 
 /// See <https://www.man7.org/linux/man-pages/man2/getrandom.2.html>.
+///
+/// Do not block when requesting random bytes.
+/// Will set `errno` to `EAGAIN` if requested entropy is not available.
 pub const GRND_NONBLOCK: c_uint = 1;
 /// See <https://www.man7.org/linux/man-pages/man2/getrandom.2.html>.
+///
+/// If this bit is set, then random bytes are drawn from the `random` source
+/// instead of the `urandom` source.
 pub const GRND_RANDOM: c_uint = 2;
 
 /// See <https://www.man7.org/linux/man-pages/man2/getrandom.2.html>.
+///
+/// Fills the buffer pointed to by `buf` with up to `buflen` random bytes.
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn getrandom(buf: *mut c_void, buflen: size_t, flags: c_uint) -> ssize_t {
     Sys::getrandom(