diff --git a/fbchat/client.py b/fbchat/client.py
index 7fb4305..3f731c9 100644
--- a/fbchat/client.py
+++ b/fbchat/client.py
@@ -495,7 +495,7 @@ class Client(object):
                 break
         return Threads  # from newest to oldest
     
-    def fetchAllUsersFromThreads(client, threads):
+    def fetchAllUsersFromThreads(self, threads):
         """
         Get all users involved in threads.