diff --git a/Lib/UserString.py b/Lib/UserString.py
index 615c135f164..c3267ad7333 100755
--- a/Lib/UserString.py
+++ b/Lib/UserString.py
@@ -232,6 +232,8 @@ class MutableString(UserString, collections.MutableSequence):
     def __imul__(self, n):
         self.data *= n
         return self
+    def insert(self, index, value):
+        self[index:index] = value
 
 collections.MutableSequence.register(MutableString)