diff --git a/slack/channels.py b/slack/channels.py
index d6f4e87..1b497c6 100644
--- a/slack/channels.py
+++ b/slack/channels.py
@@ -12,14 +12,12 @@ class Channel(threads.Thread):
     def __init__(self, json):
         threads.Thread.__init__(self, json)
         self.api_history = "channels.history"
+        self.api_mark    = "channels.mark"
         self.__member    = json.get("is_member", False)
 
     def do_fetch_info(self):
         return info(self.id())
 
-    def do_mark_messages(self, ts):
-        mark(self.id(), ts)
-
     def is_member(self):
         return self.__member
 
@@ -40,6 +38,3 @@ def list():
     for channel in ret["channels"]:
         ch_list += [ Channel(channel) ]
     return ch_list
-
-def mark(channel, timestamp):
-    api.call("channels.mark", token = auth.token(), channel = channel, ts = timestamp)
diff --git a/slack/groups.py b/slack/groups.py
index 94d6fd9..949fd03 100644
--- a/slack/groups.py
+++ b/slack/groups.py
@@ -10,13 +10,11 @@ class Group(threads.Thread):
     def __init__(self, json):
         threads.Thread.__init__(self, json)
         self.api_history = "groups.history"
+        self.api_mark    = "groups.mark"
 
     def do_fetch_info(self):
         return info(self.id())
 
-    def do_mark_messages(self, ts):
-        mark(self.id(), ts)
-
 
 
 def info(group):
@@ -34,6 +32,3 @@ def list():
     for group in ret["groups"]:
         gr_list += [ Group(group) ]
     return gr_list
-
-def mark(group, timestamp):
-    api.call("groups.mark", token = auth.token(), channel = group, ts = timestamp)
diff --git a/slack/im.py b/slack/im.py
index 055fc4c..1a72411 100644
--- a/slack/im.py
+++ b/slack/im.py
@@ -10,6 +10,7 @@ class IM(threads.Thread):
     def __init__(self, json):
         threads.Thread.__init__(self, json)
         self.api_history = "im.history"
+        self.api_mark    = "im.mark"
         self.__uid       = json.get("user")
         self.__user      = users.info(self.__uid)
 
@@ -22,9 +23,6 @@ class IM(threads.Thread):
     def do_fetch_info(self):
         return info(self.id(), self.__uid)
 
-    def do_mark_messages(self, ts):
-        mark(self.id(), ts)
-
 
 
 def info(im, uid):
@@ -42,6 +40,3 @@ def list():
     for im in ret["ims"]:
         im_list += [ IM(im) ]
     return im_list
-
-def mark(im, timestamp):
-    api.call("im.mark", token = auth.token(), channel = im, ts = timestamp)
diff --git a/slack/threads.py b/slack/threads.py
index d9c607f..eaa74e5 100644
--- a/slack/threads.py
+++ b/slack/threads.py
@@ -9,9 +9,9 @@ from . import chat
 # This class represents a slack "thread", which could be a channel, group,
 # or chat.  Note that child classes need to define the following variables:
 #
-# - do_fetch_info():     Call <whatever>.info to find unread count and timestamp.
-# - self.api_history:    The slack api method to find unread messages
-# - do_mark_messages():  Call <whatever>.mark to set unread cursor.
+# - do_fetch_info():  Call <whatever>.info to find unread count and timestamp.
+# - self.api_history: The slack api method to find unread messages
+# - self.api_mark:    Call <whatever>.mark to set unread cursor.
 #
 class Thread:
     def __init__(self, json):
@@ -42,6 +42,10 @@ class Thread:
             return None
         return json["messages"]
 
+    def mark_messages(self, stamp):
+        api.call(self.api_mark, token = auth.token(),
+                                channel = self.__id, ts = stamp)
+
     def id(self):
         return self.__id
 
@@ -73,7 +77,7 @@ class Thread:
             else:
                 m_list += [ msg ]
 
-        self.do_mark_messages(m_list[-1].ts())
+        self.mark_messages(m_list[-1].ts())
         return m_list
 
     def unread_count(self):