diff --git a/package.json b/package.json
index d3124e8..ab1fa84 100644
--- a/package.json
+++ b/package.json
@@ -40,7 +40,7 @@
     "millisecond": "~0.1.2"
   },
   "devDependencies": {
-    "assume": "~1.5.0",
+    "assume": "~2.0.0",
     "istanbul": "~0.4.5",
     "mocha": "~3.1.2",
     "pre-commit": "~1.2.0",