diff --git a/package.json b/package.json
index 826f5c9..5ed5c84 100644
--- a/package.json
+++ b/package.json
@@ -39,7 +39,7 @@
   "devDependencies": {
     "bootstrap": "^3.3.2",
     "expect.js": "~0.3.1",
-    "gregorian-calendar": "3.x",
+    "gregorian-calendar": "4.x",
     "gregorian-calendar-format": "3.x",
     "pre-commit": "1.x",
     "rc-calendar": "~3.16.1",