diff --git a/src/test/run-pass/type-sizes.rs b/src/test/run-pass/type-sizes.rs
index bbb01eaaf46..6614a76107f 100644
--- a/src/test/run-pass/type-sizes.rs
+++ b/src/test/run-pass/type-sizes.rs
@@ -31,6 +31,10 @@ enum e3 {
     a([u16; 0], u8), b
 }
 
+// Test struct field reordering to make sure it actually reorders.
+struct WillOptimize1(u8, u16, u8);
+struct WillOptimize2 { a: u8, b: u16, c: u8}
+
 pub fn main() {
     assert_eq!(size_of::<u8>(), 1 as usize);
     assert_eq!(size_of::<u32>(), 4 as usize);
@@ -54,4 +58,7 @@ pub fn main() {
     assert_eq!(size_of::<e1>(), 8 as usize);
     assert_eq!(size_of::<e2>(), 8 as usize);
     assert_eq!(size_of::<e3>(), 4 as usize);
+
+    assert_eq!(size_of::<WillOptimize1>(), 4);
+    assert_eq!(size_of::<WillOptimize2>(), 4);
 }