diff --git a/src/test/ui/run-pass/issues/issue-39720.stderr b/src/test/ui/run-pass/issues/issue-39720.stderr
new file mode 100644
index 0000000000000..7b717d86335b0
--- /dev/null
+++ b/src/test/ui/run-pass/issues/issue-39720.stderr
@@ -0,0 +1,16 @@
+warning[E0566]: conflicting representation hints
+  --> $DIR/issue-39720.rs:18:8
+   |
+LL | #[repr(C)]
+   |        ^
+LL | #[repr(simd)]
+   |        ^^^^
+
+warning[E0566]: conflicting representation hints
+  --> $DIR/issue-39720.rs:23:8
+   |
+LL | #[repr(C)]
+   |        ^
+LL | #[repr(simd)]
+   |        ^^^^
+