diff --git a/Lib/StringIO.py b/Lib/StringIO.py
index 7d57d80..9394360 100644
--- a/Lib/StringIO.py
+++ b/Lib/StringIO.py
@@ -139,7 +139,7 @@
         return r
 
     def readline(self, length=None):
-        """Read one entire line from the file.
+        r"""Read one entire line from the file.
 
         A trailing newline character is kept in the string (but may be absent
         when a file ends with an incomplete line). If the size argument is