diff --git a/notebook/auth/login.py b/notebook/auth/login.py
index 1ac434dc5e..16c4e7a356 100644
--- a/notebook/auth/login.py
+++ b/notebook/auth/login.py
@@ -112,7 +112,7 @@ def set_login_cookie(cls, handler, user_id=None):
         handler.set_secure_cookie(handler.cookie_name, user_id, **cookie_options)
         return user_id
 
-    auth_header_pat = re.compile('token\s+(.+)', re.IGNORECASE)
+    auth_header_pat = re.compile(r'token\s+(.+)', re.IGNORECASE)
 
     @classmethod
     def get_token(cls, handler):