diff --git a/activemodel/lib/active_model/observing.rb b/activemodel/lib/active_model/observing.rb
index 32f2aa46bd..29687866e3 100644
--- a/activemodel/lib/active_model/observing.rb
+++ b/activemodel/lib/active_model/observing.rb
@@ -69,8 +69,8 @@ module ActiveModel
       end
 
       # Notify list of observers of a change.
-      def notify_observers(*arg)
-        observer_instances.each { |observer| observer.update(*arg) }
+      def notify_observers(*args)
+        observer_instances.each { |observer| observer.update(*args) }
       end
 
       # Total number of observers.