diff --git a/plugins/mongodb/mongo_lag b/plugins/mongodb/mongo_lag
index 534e61d9..e85653cc 100755
--- a/plugins/mongodb/mongo_lag
+++ b/plugins/mongodb/mongo_lag
@@ -30,8 +30,9 @@ def _get_members():
 
     members = {}
     for member in repl_status['members']:
-        name = member['name'].split('.')[0]
-        members[name] = {'state': member['state'], 'optimeDate': member['optimeDate']}
+        if member['stateStr'] != 'ARBITER' :
+            name = member['name'].split('.')[0]
+            members[name] = {'state': member['state'], 'optimeDate': member['optimeDate']}
     return members
 
 def run():
@@ -42,7 +43,7 @@ def run():
 
     for member in members:
         lag = (primary_optime - members[member]['optimeDate']).seconds
-        print "{}.value {}".format(member, lag)
+        print "{0}.value {1}".format(member, lag)
 
 def config():
     print """graph_title MongoDB replication lag