diff --git a/html5lib/_inputstream.py b/html5lib/_inputstream.py
index c60d1a47..177f0ab9 100644
--- a/html5lib/_inputstream.py
+++ b/html5lib/_inputstream.py
@@ -48,7 +48,7 @@
                                   0xDFFFF, 0xEFFFE, 0xEFFFF, 0xFFFFE, 0xFFFFF,
                                   0x10FFFE, 0x10FFFF])
 
-ascii_punctuation_re = re.compile("[\u0009-\u000D\u0020-\u002F\u003A-\u0040\u005B-\u0060\u007B-\u007E]")
+ascii_punctuation_re = re.compile("[\u0009-\u000D\u0020-\u002F\u003A-\u0040\u005C\u005B-\u0060\u007B-\u007E]")
 
 # Cache for charsUntil()
 charsUntilRegEx = {}