Fix verb tense.
diff --git a/Doc/library/base64.rst b/Doc/library/base64.rst
index ab85436..c9ce28b 100644
--- a/Doc/library/base64.rst
+++ b/Doc/library/base64.rst
@@ -93,7 +93,7 @@
digit 0 is always mapped to the letter O). For security purposes the default is
``None``, so that 0 and 1 are not allowed in the input.
- The decoded string is returned. A :exc:`TypeError` is raised if *s* were
+ The decoded string is returned. A :exc:`TypeError` is raised if *s* is
incorrectly padded or if there are non-alphabet characters present in the
string.