diff --git a/package.json b/package.json
index febda8ef..5a1a53d1 100644
--- a/package.json
+++ b/package.json
@@ -28,7 +28,7 @@
     "travis-cov": "*",
     "coveralls": "*",
     "mocha-lcov-reporter": "*",
-    "muk": "*",
+    "muk": "0.5.1",
     "rewire": "*",
     "istanbul": "*"
   },