diff --git a/source/application/collision_ctrl.c b/source/application/collision_ctrl.c
index 002fc7f..e3a54a1 100644
--- a/source/application/collision_ctrl.c
+++ b/source/application/collision_ctrl.c
@@ -56,7 +56,7 @@ static void collision_ctrl_loop(void *arg)
 				sprintf(print_buffer, "start turning...\r\n");
 				shell_write(print_buffer, strlen(print_buffer));
 				drive_ctrl_turn_left();
-				sleep_ms(drv_read(&rng, Null, 0) % 3500 + 500); // rand between 500 and 4000
+				sleep_ms(drv_read(&rng, NULL, 0) % 3500 + 500); // rand between 500 and 4000
 				drive_ctrl_halt();
 
 				sprintf(print_buffer, "restart forward...\r\n");