diff --git a/selfdrive/controls/controlsd.py b/selfdrive/controls/controlsd.py
index 1a911ef985..b613983bfd 100755
--- a/selfdrive/controls/controlsd.py
+++ b/selfdrive/controls/controlsd.py
@@ -740,7 +740,7 @@ class Controls:
     self.prof.checkpoint("Sent")
 
     self.update_button_timers(CS.buttonEvents)
-    self.CS_prev = CS
+    self.CS_prev = CS.as_reader()
 
   def controlsd_thread(self):
     while True: