diff --git a/src/modules/commander/state_machine_helper.cpp b/src/modules/commander/state_machine_helper.cpp
index 40aa4a2f0c..0154f235f6 100644
--- a/src/modules/commander/state_machine_helper.cpp
+++ b/src/modules/commander/state_machine_helper.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
  *
- *   Copyright (c) 2013, 2014 PX4 Development Team. All rights reserved.
+ *   Copyright (c) 2013-2015 PX4 Development Team. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -35,7 +35,7 @@
  * @file state_machine_helper.cpp
  * State machine helper functions implementations
  *
- * @author Thomas Gubler <thomasgubler@student.ethz.ch>
+ * @author Thomas Gubler <thomas@px4.io>
  * @author Julian Oes <julian@oes.ch>
  */
 
diff --git a/src/modules/sensors/sensor_params.c b/src/modules/sensors/sensor_params.c
index 3e21ec2a91..5ec6780331 100644
--- a/src/modules/sensors/sensor_params.c
+++ b/src/modules/sensors/sensor_params.c
@@ -130,7 +130,7 @@ PARAM_DEFINE_INT32(CAL_MAG0_ID, 0);
  * @max 30
  * @group Sensor Calibration
  */
-PARAM_DEFINE_INT32(CAL_MAG0_ROT, 0);
+PARAM_DEFINE_INT32(CAL_MAG0_ROT, -1);
 
 /**
  * Magnetometer X-axis offset
@@ -308,7 +308,7 @@ PARAM_DEFINE_INT32(CAL_MAG1_ID, 0);
  * @max 30
  * @group Sensor Calibration
  */
-PARAM_DEFINE_INT32(CAL_MAG1_ROT, 0);
+PARAM_DEFINE_INT32(CAL_MAG1_ROT, -1);
 
 /**
  * Magnetometer X-axis offset
@@ -486,7 +486,7 @@ PARAM_DEFINE_INT32(CAL_MAG2_ID, 0);
  * @max 30
  * @group Sensor Calibration
  */
-PARAM_DEFINE_INT32(CAL_MAG2_ROT, 0);
+PARAM_DEFINE_INT32(CAL_MAG2_ROT, -1);
 
 /**
  * Magnetometer X-axis offset
diff --git a/src/modules/sensors/sensors.cpp b/src/modules/sensors/sensors.cpp
index 9a90c84e04..1d392b0daa 100644
--- a/src/modules/sensors/sensors.cpp
+++ b/src/modules/sensors/sensors.cpp
@@ -1511,14 +1511,21 @@ Sensors::parameter_update_poll(bool forced)
 					if (ioctl(fd, MAGIOCGEXTERNAL, 0) <= 0) {
 						/* mag is internal */
 						_mag_rotation[s] = _board_rotation;
-						/* reset param to -1 to indicate external mag */
+						/* reset param to -1 to indicate internal mag */
 						int32_t minus_one = MAG_ROT_VAL_INTERNAL;
 						param_set_no_notification(param_find(str), &minus_one);
 					} else {
 
-						int32_t mag_rot = 0;
+						int32_t mag_rot;
 						param_get(param_find(str), &mag_rot);
 
+						/* check if this mag is still set as internal */
+						if (mag_rot < 0) {
+							/* it was marked as internal, change to external with no rotation */
+							mag_rot = 0;
+							param_set_no_notification(param_find(str), &mag_rot);
+						}
+
 						/* handling of old setups, will be removed later (noted Feb 2015) */
 						int32_t deprecated_mag_rot = 0;
 						param_get(param_find("SENS_EXT_MAG_ROT"), &deprecated_mag_rot);