diff --git a/lib/utils/mutate.js b/lib/utils/mutate.js
index 83bf19c..3d4b78d 100644
--- a/lib/utils/mutate.js
+++ b/lib/utils/mutate.js
@@ -25,7 +25,7 @@ utils.mutate = {
         return p1 + make.unit.unit()
       }
     }
-    return str.replace(/(\d*)(px|em|ex|ch|rem|mm|cm|in|pt|pc|%')/g, mutator)
+    return str.replace(/(\d+)(px|em|ex|ch|rem|mm|cm|in|pt|pc|%')/g, mutator)
   },
 
   random: function (str) {