diff --git a/robomaster_pi/conn_vel.py b/robomaster_pi/conn_vel.py
index 49e2b8d32807afc35042348dbbef1890fdf6b7e6..5accc93909d5e3d99ddd9afb9aeb61e7fc91f5be 100644
--- a/robomaster_pi/conn_vel.py
+++ b/robomaster_pi/conn_vel.py
@@ -32,7 +32,7 @@ class vel_from_ros_node(Node):
         self.get_vel_from_ros_ = self.create_subscription(Twist, "/cmd_vel", self.pose_callback, 10)
 
 
-    def check_connection(args):
+    def check_connection(self, args):
         print("ja")
         self.response = self.isConnected()
         if(self.response != True):