remove dup flag
diff --git a/stack.sh b/stack.sh
index ccddea1..a88888c 100755
--- a/stack.sh
+++ b/stack.sh
@@ -221,7 +221,6 @@
 add_nova_flag "--vncproxy_wwwroot=$NOVNC_DIR/"
 add_nova_flag "--api_paste_config=$KEYSTONE_DIR/examples/paste/nova-api-paste.ini"
 add_nova_flag "--image_service=nova.image.glance.GlanceImageService"
-add_nova_flag "--image_service=nova.image.glance.GlanceImageService"
 add_nova_flag "--ec2_dmz_host=$EC2_DMZ_HOST"
 add_nova_flag "--rabbit_host=$RABBIT_HOST"
 add_nova_flag "--glance_api_servers=$GLANCE_HOSTPORT"