diff --git a/rpi/ProotState.py b/rpi/ProotState.py
index a3ee884..2ffed7e 100644
--- a/rpi/ProotState.py
+++ b/rpi/ProotState.py
@@ -80,7 +80,7 @@ class ProotState:
             matrix.SwapOnVSync(self.frame_canvas_prootScreen_3)
 
 
-    def update_screen(blinkFrameCanvases, matrix):
+    def update_screen(self, blinkFrameCanvases, matrix):
 
         proot_state = ProotState()