diff --git a/user/super/com/google/gwt/emul/java/util/Arrays.java b/user/super/com/google/gwt/emul/java/util/Arrays.java
index a9dd2a4acdf..f3e1e4e6700 100644
--- a/user/super/com/google/gwt/emul/java/util/Arrays.java
+++ b/user/super/com/google/gwt/emul/java/util/Arrays.java
@@ -1774,6 +1774,7 @@ private static CompareDoubleFunction getDoubleComparator() {
 
   @JsFunction
   private interface CompareLongFunction {
+    @SuppressWarnings("unusable-by-js")
     int compare(long d1, long d2);
   }