diff --git a/selfdrive/controls/lib/drive_helpers.py b/selfdrive/controls/lib/drive_helpers.py
index 038061b7e6..3f99f1bbbb 100644
--- a/selfdrive/controls/lib/drive_helpers.py
+++ b/selfdrive/controls/lib/drive_helpers.py
@@ -19,8 +19,8 @@ def clamp(val, min_val, max_val):
   clamped_val = float(np.clip(val, min_val, max_val))
   return clamped_val, clamped_val != val
 
-def smooth_value(val, prev_val, tau):
-  alpha = 1 - np.exp(-DT_MDL / tau) if tau > 0 else 1
+def smooth_value(val, prev_val, tau, dt=DT_MDL):
+  alpha = 1 - np.exp(-dt/tau) if tau > 0 else 1
   return alpha * val + (1 - alpha) * prev_val
 
 def clip_curvature(v_ego, prev_curvature, new_curvature, roll):