diff --git a/selfdrive/controls/lib/longitudinal_mpc_lib/long_mpc.py b/selfdrive/controls/lib/longitudinal_mpc_lib/long_mpc.py
index e75e84da1..740152636 100644
--- a/selfdrive/controls/lib/longitudinal_mpc_lib/long_mpc.py
+++ b/selfdrive/controls/lib/longitudinal_mpc_lib/long_mpc.py
@@ -352,7 +352,7 @@ class LongitudinalMpc():
     x_obstacle = 1e5*np.ones((N+1))
     self.params = np.concatenate([self.accel_limit_arr,
                              x_obstacle[:,None],
-                             self.prev_a], axis=1)
+                             self.prev_a[:,None]], axis=1)
     self.run()