diff --git a/crates/core_arch/src/x86_64/amx.rs b/crates/core_arch/src/x86_64/amx.rs
index 3e0ac8f47c..f372f7066d 100644
--- a/crates/core_arch/src/x86_64/amx.rs
+++ b/crates/core_arch/src/x86_64/amx.rs
@@ -510,7 +510,7 @@ mod tests {
     use syscalls::{Sysno, syscall};
 
     #[allow(non_camel_case_types)]
-    #[repr(packed)]
+    #[repr(C, packed)]
     #[derive(Copy, Clone, Default, Debug, PartialEq)]
     struct __tilecfg {
         /// 0 `or` 1