diff --git a/tests/codegen/lib-optimizations/iter-sum.rs b/tests/codegen/lib-optimizations/iter-sum.rs
index d6ea4cd74d5..ff7ca6ef6c1 100644
--- a/tests/codegen/lib-optimizations/iter-sum.rs
+++ b/tests/codegen/lib-optimizations/iter-sum.rs
@@ -1,5 +1,6 @@
 // ignore-debug: the debug assertions get in the way
 // compile-flags: -O
+// only-x86_64 (vectorization varies between architectures)
 #![crate_type = "lib"]