diff --git a/src/rfc3986/abnf_regexp.py b/src/rfc3986/abnf_regexp.py
index 6d02c66..00ff99e 100644
--- a/src/rfc3986/abnf_regexp.py
+++ b/src/rfc3986/abnf_regexp.py
@@ -42,7 +42,7 @@
 _AUTHORITY_RE = "[^\\\\/?#]*"
 _PATH_RE = "[^?#]*"
 _QUERY_RE = "[^#]*"
-_FRAGMENT_RE = "[\S\s]*"
+_FRAGMENT_RE = r"[\S\s]*"
 
 # Extracted from http://tools.ietf.org/html/rfc3986#appendix-B
 COMPONENT_PATTERN_DICT = {