diff --git a/stdlib/2/string.pyi b/stdlib/2/string.pyi
index fc06f1a0c..ecdf23fc1 100644
--- a/stdlib/2/string.pyi
+++ b/stdlib/2/string.pyi
@@ -52,13 +52,13 @@ class Template:
 
     def __init__(self, template: Text) -> None: ...
     @overload
-    def substitute(self, mapping: Mapping[Text, str] = ..., **kwds: str) -> str: ...
+    def substitute(self, mapping: Union[Mapping[str, str], Mapping[unicode, str]] = ..., **kwds: str) -> str: ...
     @overload
-    def substitute(self, mapping: Mapping[Text, Text] = ..., **kwds: Text) -> Text: ...
+    def substitute(self, mapping: Union[Mapping[str, Text], Mapping[unicode, Text]] = ..., **kwds: Text) -> Text: ...
     @overload
-    def safe_substitute(self, mapping: Mapping[Text, str] = ..., **kwds: str) -> str: ...
+    def safe_substitute(self, mapping: Union[Mapping[str, str], Mapping[unicode, str]] = ..., **kwds: str) -> str: ...
     @overload
-    def safe_substitute(self, mapping: Mapping[Text, Text] = ..., **kwds: Text) -> Text: ...
+    def safe_substitute(self, mapping: Union[Mapping[str, Text], Mapping[unicode, Text]], **kwds: Text) -> Text: ...
 
 # TODO(MichalPokorny): This is probably badly and/or loosely typed.
 class Formatter(object):