diff --git a/django/utils/regex_helper.py b/django/utils/regex_helper.py
index e910cac4aa..8612475b96 100644
--- a/django/utils/regex_helper.py
+++ b/django/utils/regex_helper.py
@@ -341,7 +341,7 @@ def _lazy_re_compile(regex, flags=0):
     """Lazily compile a regex with flags."""
     def _compile():
         # Compile the regex if it was not passed pre-compiled.
-        if isinstance(regex, str):
+        if isinstance(regex, (str, bytes)):
             return re.compile(regex, flags)
         else:
             assert not flags, (