# Fix a syntax warning, similar to upstream PR 307
--- a/test/testlex.py
+++ b/test/testlex.py
@@ -191,7 +191,7 @@
                    "Make sure '#' in rule 't_POUND' is escaped with '\\#'\n")
         else:
             msg = ("Invalid regular expression for rule 't_POUND'. missing ), unterminated subpattern at position 0\n"
-                   "ERROR: Make sure '#' in rule 't_POUND' is escaped with '\#'")
+                   r"ERROR: Make sure '#' in rule 't_POUND' is escaped with '\#'")
         self.assertTrue(check_expected(result,
                                     msg,
                                     contains=True), result)
