diff --git a/lib/matplotlib/docstring.py b/lib/matplotlib/docstring.py
index 626137a52439..cf9537f0c6fe 100644
--- a/lib/matplotlib/docstring.py
+++ b/lib/matplotlib/docstring.py
@@ -87,7 +87,7 @@ def __init__(self, addendum, join=''):
 
     def __call__(self, func):
         docitems = [func.__doc__, self.addendum]
-        func.__doc__ = func.__doc__ and ''.join(docitems)
+        func.__doc__ = func.__doc__ and self.join.join(docitems)
         return func