diff --git a/src/process.rs b/src/process.rs
index 8e184bbe..39004ae4 100644
--- a/src/process.rs
+++ b/src/process.rs
@@ -8,13 +8,20 @@ use std::os::unix::process::ExitStatusExt;
 use std::os::windows::process::ExitStatusExt;
 use std::{num::NonZeroU32, os::raw::c_int, process::ExitStatus, ptr::null};
 
-use rb_sys::{pid_t, rb_sys_fail, rb_waitpid};
+use rb_sys::{rb_sys_fail, rb_waitpid};
 
 use crate::{
     api::Ruby,
     error::{protect, Error},
 };
 
+#[allow(non_camel_case_types)]
+#[cfg(unix)]
+type rb_pid_t = c_int;
+#[allow(non_camel_case_types)]
+#[cfg(windows)]
+type rb_pid_t = i64;
+
 /// # Process
 ///
 /// Functions for working with processes.
@@ -98,12 +105,12 @@ pub enum WaitTarget {
 }
 
 impl WaitTarget {
-    fn to_rb_pid_t(self) -> pid_t {
+    fn to_rb_pid_t(self) -> rb_pid_t {
         match self {
-            Self::ChildPid(pid) => pid as pid_t,
+            Self::ChildPid(pid) => pid as rb_pid_t,
             Self::ProcessGroup => 0,
             Self::AnyChild => -1,
-            Self::ChildProcessGroup(pid) => -(pid as pid_t),
+            Self::ChildProcessGroup(pid) => -(pid as rb_pid_t),
         }
     }
 }