diff --git a/Lib/email/base64mime.py b/Lib/email/base64mime.py
index 6db007dc197..5131f8e13e8 100644
--- a/Lib/email/base64mime.py
+++ b/Lib/email/base64mime.py
@@ -113,7 +113,7 @@ def decode(string):
     elif isinstance(string, str):
         return a2b_base64(string.encode('raw-unicode-escape'))
     else:
-        return a2b_base64(s)
+        return a2b_base64(string)
 
 
 # For convenience and backwards compatibility w/ standard base64 module