better message

alecthomas · Oct 17, 2016 · c2e01a1 · c2e01a1
1 parent 77086ae
commit c2e01a1
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/voluptuous/validators.py b/voluptuous/validators.py
@@ -465,7 +465,7 @@ def __init__(self, kind):
 
     def __call__(self, v):
         if v is not None and not isinstance(v, self.kind):
-            raise Invalid("%s not of type %s" % (v, self.kind))
+            raise Invalid("%s must be None or of type %s" % (v, self.kind))
 
         return v