diff --git a/library/std/src/sys/windows/os_str.rs b/library/std/src/sys/windows/os_str.rs
index 78e92a3331a1c..11883f15022f6 100644
--- a/library/std/src/sys/windows/os_str.rs
+++ b/library/std/src/sys/windows/os_str.rs
@@ -44,6 +44,7 @@ impl fmt::Display for Buf {
     }
 }
 
+#[repr(transparent)]
 pub struct Slice {
     pub inner: Wtf8,
 }