diff --git a/ArduCopter/system.pde b/ArduCopter/system.pde
index 53bbe591da..3537aff61b 100644
--- a/ArduCopter/system.pde
+++ b/ArduCopter/system.pde
@@ -203,7 +203,9 @@ static void init_ardupilot()
 
 	init_camera();
 
+#if HIL_MODE != HIL_MODE_ATTITUDE
     timer_scheduler.init( &isr_registry );
+#endif
 
 #if HIL_MODE != HIL_MODE_ATTITUDE
 #if CONFIG_ADC == ENABLED
diff --git a/ArduPlane/system.pde b/ArduPlane/system.pde
index 676f4f418a..41dcd06edb 100644
--- a/ArduPlane/system.pde
+++ b/ArduPlane/system.pde
@@ -91,7 +91,9 @@ static void init_ardupilot()
 	// Initialize the timer scheduler to use the ISR registry.
 	//
 
+#if HIL_MODE != HIL_MODE_ATTITUDE
     timer_scheduler.init( & isr_registry );
+#endif
 
 	//
 	// Check the EEPROM format version before loading any parameters from EEPROM.