diff --git a/channels/binding/base.py b/channels/binding/base.py
index fb117ee..85ec720 100644
--- a/channels/binding/base.py
+++ b/channels/binding/base.py
@@ -142,7 +142,7 @@ class Binding(object):
         if action == CREATE:
             group_names = set()
         else:
-            group_names = set(cls.group_names(instance, action))
+            group_names = set(cls.group_names(instance))
 
         if not hasattr(instance, '_binding_group_names'):
             instance._binding_group_names = {}
@@ -157,7 +157,7 @@ class Binding(object):
         if action == DELETE:
             new_group_names = set()
         else:
-            new_group_names = set(cls.group_names(instance, action))
+            new_group_names = set(cls.group_names(instance))
 
         # if post delete, new_group_names should be []
         self = cls()
@@ -186,7 +186,7 @@ class Binding(object):
             group.send(message)
 
     @classmethod
-    def group_names(cls, instance, action):
+    def group_names(cls, instance):
         """
         Returns the iterable of group names to send the object to based on the
         instance and action performed on it.
diff --git a/channels/tests/test_binding.py b/channels/tests/test_binding.py
index 2383cfb..6b32a02 100644
--- a/channels/tests/test_binding.py
+++ b/channels/tests/test_binding.py
@@ -21,7 +21,7 @@ class TestsBinding(ChannelTestCase):
             fields = ['username', 'email', 'password', 'last_name']
 
             @classmethod
-            def group_names(cls, instance, action):
+            def group_names(cls, instance):
                 return ["users"]
 
             def has_permission(self, user, action, pk):
@@ -62,7 +62,7 @@ class TestsBinding(ChannelTestCase):
             exclude = ['first_name', 'last_name']
 
             @classmethod
-            def group_names(cls, instance, action):
+            def group_names(cls, instance):
                 return ["users_exclude"]
 
             def has_permission(self, user, action, pk):
@@ -105,7 +105,7 @@ class TestsBinding(ChannelTestCase):
                 stream = 'test'
 
                 @classmethod
-                def group_names(cls, instance, action):
+                def group_names(cls, instance):
                     return ["users_omit"]
 
                 def has_permission(self, user, action, pk):
@@ -119,7 +119,7 @@ class TestsBinding(ChannelTestCase):
             fields = ['__all__']
 
             @classmethod
-            def group_names(cls, instance, action):
+            def group_names(cls, instance):
                 return ["users2"]
 
             def has_permission(self, user, action, pk):
@@ -164,7 +164,7 @@ class TestsBinding(ChannelTestCase):
             fields = ['username']
 
             @classmethod
-            def group_names(cls, instance, action):
+            def group_names(cls, instance):
                 return ["users3"]
 
             def has_permission(self, user, action, pk):
@@ -203,7 +203,7 @@ class TestsBinding(ChannelTestCase):
             fields = ['username', 'email', 'password', 'last_name']
 
             @classmethod
-            def group_names(cls, instance, action):
+            def group_names(cls, instance):
                 return ['users_outbound']
 
             def has_permission(self, user, action, pk):
@@ -243,7 +243,7 @@ class TestsBinding(ChannelTestCase):
             fields = ['username', ]
 
             @classmethod
-            def group_names(cls, instance, action):
+            def group_names(cls, instance):
                 return ['users_outbound']
 
             def has_permission(self, user, action, pk):
@@ -289,7 +289,7 @@ class TestsBinding(ChannelTestCase):
             fields = ['username', ]
 
             @classmethod
-            def group_names(cls, instance, action):
+            def group_names(cls, instance):
                 return ['users_outbound']
 
             def has_permission(self, user, action, pk):