diff --git a/libraries/AP_HAL_PX4/HAL_PX4_Class.cpp b/libraries/AP_HAL_PX4/HAL_PX4_Class.cpp
index 57bc46c5de..b2ddab671e 100644
--- a/libraries/AP_HAL_PX4/HAL_PX4_Class.cpp
+++ b/libraries/AP_HAL_PX4/HAL_PX4_Class.cpp
@@ -82,7 +82,8 @@ HAL_PX4::HAL_PX4() :
         &rcinDriver,  /* rcinput */
         &rcoutDriver, /* rcoutput */
         &schedulerInstance, /* scheduler */
-        &utilInstance) /* util */
+        &utilInstance, /* util */
+        NULL)    /* no onboard optical flow */
 {}
 
 bool _px4_thread_should_exit = false;        /**< Daemon exit flag */