diff --git a/js/src/jsexn.c b/js/src/jsexn.c
index 09d10a29aa6..74030db63ae 100644
--- a/js/src/jsexn.c
+++ b/js/src/jsexn.c
@@ -909,7 +909,7 @@ js_GetLocalizedErrorMessage(JSContext* cx, void *userRef, const char *locale, co
 {
     const JSErrorFormatString *errorString = NULL;
 
-    if (cx->localeCallbacks) {
+    if (cx->localeCallbacks && cx->localeCallbacks->localeGetErrorMessage) {
         errorString = cx->localeCallbacks
                         ->localeGetErrorMessage(userRef, locale, errorNumber);
     }