diff --git a/pyoo.py b/pyoo.py
index 37f0fc9..d432da1 100644
--- a/pyoo.py
+++ b/pyoo.py
@@ -1937,7 +1937,7 @@ def open_spreadsheet(self, path, as_template=False):
 
 
 class NameGenerator(object):
-    """
+    r"""
     Generates valid names for Open Office.
 
     Keeps track of used names and does not return one value twice.
@@ -1954,7 +1954,7 @@ def __init__(self):
 
     def __call__(self, name):
         name = text_type(name)
-        for char in '[]*?:\/':
+        for char in r'[]*?:\/':
             name = name.replace(char, '')
         for i in itertools.count(1):
             if name: