diff --git a/src/modules/sensors/sensor_params.c b/src/modules/sensors/sensor_params.c
index a80ca4eb64..3e21ec2a91 100644
--- a/src/modules/sensors/sensor_params.c
+++ b/src/modules/sensors/sensor_params.c
@@ -122,6 +122,12 @@ PARAM_DEFINE_INT32(CAL_MAG0_ID, 0);
 /**
  * Rotation of magnetometer 0 relative to airframe.
  *
+ * An internal magnetometer will force a value of -1, so a GCS
+ * should only attempt to configure the rotation if the value is
+ * greater than or equal to zero.
+ *
+ * @min -1
+ * @max 30
  * @group Sensor Calibration
  */
 PARAM_DEFINE_INT32(CAL_MAG0_ROT, 0);
@@ -292,8 +298,14 @@ PARAM_DEFINE_FLOAT(CAL_GYRO1_ZSCALE, 1.0f);
 PARAM_DEFINE_INT32(CAL_MAG1_ID, 0);
 
 /**
- * Rotation of magnetometer 0 relative to airframe.
+ * Rotation of magnetometer 1 relative to airframe.
  *
+ * An internal magnetometer will force a value of -1, so a GCS
+ * should only attempt to configure the rotation if the value is
+ * greater than or equal to zero.
+ *
+ * @min -1
+ * @max 30
  * @group Sensor Calibration
  */
 PARAM_DEFINE_INT32(CAL_MAG1_ROT, 0);
@@ -464,8 +476,14 @@ PARAM_DEFINE_FLOAT(CAL_GYRO2_ZSCALE, 1.0f);
 PARAM_DEFINE_INT32(CAL_MAG2_ID, 0);
 
 /**
- * Rotation of magnetometer 0 relative to airframe.
+ * Rotation of magnetometer 2 relative to airframe.
  *
+ * An internal magnetometer will force a value of -1, so a GCS
+ * should only attempt to configure the rotation if the value is
+ * greater than or equal to zero.
+ *
+ * @min -1
+ * @max 30
  * @group Sensor Calibration
  */
 PARAM_DEFINE_INT32(CAL_MAG2_ROT, 0);
diff --git a/src/modules/sensors/sensors.cpp b/src/modules/sensors/sensors.cpp
index f9a607d77d..7d60bf563b 100644
--- a/src/modules/sensors/sensors.cpp
+++ b/src/modules/sensors/sensors.cpp
@@ -134,16 +134,16 @@
 #define ADC_AIRSPEED_VOLTAGE_CHANNEL	-1
 #endif
 
-#define BATT_V_LOWPASS 0.001f
-#define BATT_V_IGNORE_THRESHOLD 4.8f
+#define BATT_V_LOWPASS			0.001f
+#define BATT_V_IGNORE_THRESHOLD		4.8f
 
 /**
  * HACK - true temperature is much less than indicated temperature in baro,
  * subtract 5 degrees in an attempt to account for the electrical upheating of the PCB
  */
-#define PCB_TEMP_ESTIMATE_DEG 5.0f
-
-#define STICK_ON_OFF_LIMIT 0.75f
+#define PCB_TEMP_ESTIMATE_DEG		5.0f
+#define STICK_ON_OFF_LIMIT		0.75f
+#define MAG_ROT_VAL_INTERNAL		-1
 
 /* oddly, ERROR is not defined for c++ */
 #ifdef ERROR
@@ -1515,6 +1515,9 @@ 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 */
+						int32_t minus_one = MAG_ROT_VAL_INTERNAL;
+						param_set(param_find("CAL_MAG0_ROT"), &minus_one);
 					} else {
 
 						int32_t mag_rot = 0;
@@ -1527,12 +1530,17 @@ Sensors::parameter_update_poll(bool forced)
 							param_get(param_find("SENS_EXT_MAG_ROT"), &deprecated_mag_rot);
 
 							/* if the old param is non-zero, set the new one to the same value */
-							if ((deprecated_mag_rot != 0) && (mag_rot == 0)) {
+							if ((deprecated_mag_rot != 0) && (mag_rot <= 0)) {
 								mag_rot = deprecated_mag_rot;
 								param_set(param_find("CAL_MAG0_ROT"), &mag_rot);
 							}
 						}
 
+						/* handling of transition from internal to external */
+						if (mag_rot < 0) {
+							mag_rot = 0;
+						}
+
 						get_rot_matrix((enum Rotation)mag_rot, &_mag_rotation[s]);
 					}