diff --git a/mh_utils/cef_parser/__init__.py b/mh_utils/cef_parser/__init__.py
index 207abc2..306b6f4 100644
--- a/mh_utils/cef_parser/__init__.py
+++ b/mh_utils/cef_parser/__init__.py
@@ -402,6 +402,7 @@ class Flag(str):
 	:param severity: The severity of the flag
 	"""
 
+	__slots__ = ("severity", )
 	severity: int
 
 	def __copy__(self):