diff --git a/hgext/mq.py b/hgext/mq.py
--- a/hgext/mq.py
+++ b/hgext/mq.py
@@ -565,7 +565,7 @@
                 return index
         return None
 
-    guard_re = re.compile(r'\s?#([-+][^-+# \t\r\n\f][^# \t\r\n\f]*)')
+    guard_re = re.compile(br'\s?#([-+][^-+# \t\r\n\f][^# \t\r\n\f]*)')
 
     def parseseries(self):
         self.series = []
diff --git a/mercurial/util.py b/mercurial/util.py
--- a/mercurial/util.py
+++ b/mercurial/util.py
@@ -2667,7 +2667,7 @@
         else:
             prefix_char = prefix
         mapping[prefix_char] = prefix_char
-    r = remod.compile(r'%s(%s)' % (prefix, patterns))
+    r = remod.compile(br'%s(%s)' % (prefix, patterns))
     return r.sub(lambda x: fn(mapping[x.group()[1:]]), s)
 
 def getport(port):