diff --git a/src/flake8/defaults.py b/src/flake8/defaults.py
index 55cb48a..3ad959b 100644
--- a/src/flake8/defaults.py
+++ b/src/flake8/defaults.py
@@ -46,7 +46,7 @@ NOQA_INLINE_REGEXP = re.compile(
     # We do not care about the ``: `` that follows ``noqa``
     # We do not care about the casing of ``noqa``
     # We want a comma-separated list of errors
-    '# noqa(?:: (?P<codes>([A-Z][0-9]+(?:[,\s]+)?)+))?',
+    r'# noqa(?:: (?P<codes>([A-Z][0-9]+(?:[,\s]+)?)+))?',
     re.IGNORECASE
 )