diff --git a/WebIDL.py b/WebIDL.py
index 0ad1f8f9215..d8f87bc332d 100644
or identifier == "RunConstructorInCallerCompartment"
or identifier == "WantsEventListenerHooks"
or identifier == "Serializable"
+ or identifier == "Abstract"
):
# Known extended attributes that do not take values
if not attr.noArguments():
--
2.51.0