diff --git a/src/unix/redox/mod.rs b/src/unix/redox/mod.rs
index 3bb7b044d0c1b..6855171990016 100644
--- a/src/unix/redox/mod.rs
+++ b/src/unix/redox/mod.rs
@@ -1,8 +1,20 @@
 pub type c_char = i8;
-pub type c_long = i64;
-pub type c_ulong = u64;
 pub type wchar_t = i32;
 
+cfg_if! {
+    if #[cfg(target_pointer_width = "32")] {
+        pub type c_long = i32;
+        pub type c_ulong = u32;
+    }
+}
+
+cfg_if! {
+    if #[cfg(target_pointer_width = "64")] {
+        pub type c_long = i64;
+        pub type c_ulong = u64;
+    }
+}
+
 pub type blkcnt_t = ::c_ulong;
 pub type blksize_t = ::c_long;
 pub type clock_t = ::c_long;