diff --git a/libraries/APM_OBC/APM_OBC.cpp b/libraries/APM_OBC/APM_OBC.cpp
index 529527c6e0..046e342497 100644
--- a/libraries/APM_OBC/APM_OBC.cpp
+++ b/libraries/APM_OBC/APM_OBC.cpp
@@ -74,6 +74,10 @@ APM_OBC::check(APM_OBC::control_mode mode,
 	// mode. This tells it to pass through controls from the
 	// receiver
 	if (_manual_pin != -1) {
+		if (_manual_pin != _last_manual_pin) {
+			pinMode(_manual_pin, OUTPUT);
+			_last_manual_pin = _manual_pin;
+		}
 		digitalWrite(_manual_pin, mode==OBC_MANUAL);
 	}
 
@@ -146,6 +150,10 @@ APM_OBC::check(APM_OBC::control_mode mode,
 
 	// if we are not terminating then toggle the heartbeat pin at 10Hz
 	if (!_terminate && _heartbeat_pin != -1) {
+		if (_heartbeat_pin != _last_heartbeat_pin) {
+			pinMode(_heartbeat_pin, OUTPUT);
+			_last_heartbeat_pin = _heartbeat_pin;
+		}
 		_heartbeat_pin_value = !_heartbeat_pin_value;
 		digitalWrite(_heartbeat_pin, _heartbeat_pin_value);
 	}	
diff --git a/libraries/APM_OBC/APM_OBC.h b/libraries/APM_OBC/APM_OBC.h
index df9df1d8f5..8d72dc3ae7 100644
--- a/libraries/APM_OBC/APM_OBC.h
+++ b/libraries/APM_OBC/APM_OBC.h
@@ -34,12 +34,8 @@ public:
 	// Constructor
 	APM_OBC(void)
 	{
-		if (_heartbeat_pin != -1) {
-			pinMode(_heartbeat_pin, OUTPUT);
-		}
-		if (_manual_pin != -1) {
-			pinMode(_manual_pin,    OUTPUT);
-		}
+		_last_heartbeat_pin = -1;
+		_last_manual_pin = -1;
 		_state = STATE_PREFLIGHT;
 		_terminate.set(0);
 
@@ -64,6 +60,10 @@ private:
 	AP_Int8 _manual_pin;
 	AP_Int8 _terminate;
 
+	// last pins to cope with changing at runtime
+	int8_t _last_heartbeat_pin;
+	int8_t _last_manual_pin;
+
 	// waypoint numbers to jump to on failsafe conditions
 	AP_Int8 _wp_comms_hold;
 	AP_Int8 _wp_gps_loss;