diff --git a/moment/moment-tests.ts b/moment/moment-tests.ts
index 9dd64d407..e993a3ad2 100644
--- a/moment/moment-tests.ts
+++ b/moment/moment-tests.ts
@@ -258,7 +258,7 @@ moment.lang('en', {
 });
 
 moment.lang('en', {
-    months : function (momentToFormat, format) {
+    months : function (momentToFormat: Moment, format: string) {
         // momentToFormat is the moment currently being formatted
         // format is the formatting string
         if (/^MMMM/.test(format)) { // if the format starts with 'MMMM'
@@ -277,7 +277,7 @@ moment.lang('en', {
 });
 
 moment.lang('en', {
-    monthsShort : function (momentToFormat, format) {
+    monthsShort : function (momentToFormat: Moment, format: string) {
         if (/^MMMM/.test(format)) {
             return this.nominative[momentToFormat.month()];
         } else {