diff --git a/settings_manager.py b/settings_manager.py
index d778978..1743f10 100644
--- a/settings_manager.py
+++ b/settings_manager.py
@@ -218,7 +218,7 @@
                 IP(value)
 
             elif key.lower() == 'mac':
-                regex = '([a-fA-F0-9]{2}[:|\-]?){6}'
+                regex = r'([a-fA-F0-9]{2}[:|\-]?){6}'
                 self.validate_regex(regex, value)
 
             elif key.lower() == 'prefix':