diff --git a/wgpu-hal/src/dx12/mod.rs b/wgpu-hal/src/dx12/mod.rs
index be0f6960ba7..a442f793990 100644
--- a/wgpu-hal/src/dx12/mod.rs
+++ b/wgpu-hal/src/dx12/mod.rs
@@ -623,7 +623,7 @@ struct PassState {
 #[test]
 fn test_dirty_mask() {
     use std::mem::size_of;
-    assert_eq!(MAX_ROOT_ELEMENTS, size_of::<u64>() * 8);
+    assert_eq!(MAX_ROOT_ELEMENTS, (u64::BITS as usize));
 }
 
 impl PassState {