diff --git a/package.json b/package.json
index ad2356e..ddd1355 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,7 @@
     "browser-resolve": "^1.11.1",
     "is-builtin-module": "^1.0.0",
     "postcss": "^6.0.0",
-    "postcss-calc": "^6.0.0",
+    "postcss-calc": "^5.0.0",
     "postcss-cssnext": "^2.0.0",
     "postcss-url": "^5.1.2",
     "css-mediaquery": "0.1.2",