diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 0f11787..f1c084f 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -1581,7 +1581,14 @@ struct JSPropertySpec {
     uintptr_t type;
     union {
       const char* string;
+#if MOZ_BIG_ENDIAN && JS_BITS_PER_WORD == 64
+      struct {
+        uint32_t padding;
+        int32_t int32;
+      };
+#else
       int32_t int32;
+#endif
     };
   };