diff --git a/pytools/diskdict.py b/pytools/diskdict.py
index 1739afaa04f07f6024e103af17a8112dc9896337..ca44098a5b53cf83e04daf99c3b0e16d54c5f9b2 100644
--- a/pytools/diskdict.py
+++ b/pytools/diskdict.py
@@ -88,7 +88,8 @@ class DiskDict(object):
                 "from the dictionary in a second run, defeating the purpose of "
                 "persisting to disk."
                 "DiskDict is deprecated and will be removed in 2018. "
-                "Use pytools.persistent_dict instead.", DeprecationWarning, stacklevel=2)
+                "Use pytools.persistent_dict instead.", DeprecationWarning,
+                stacklevel=2)
 
     def __contains__(self, key):
         if key in self.cache: