diff --git a/src/FirmwarePlugin/PX4/PX4FirmwarePlugin.cc b/src/FirmwarePlugin/PX4/PX4FirmwarePlugin.cc
index 1a7fa10953c17eba92a642067c58feda5f4266ce..979855640b69c4d85a91081962449fbbdfaa2aca 100644
--- a/src/FirmwarePlugin/PX4/PX4FirmwarePlugin.cc
+++ b/src/FirmwarePlugin/PX4/PX4FirmwarePlugin.cc
@@ -74,7 +74,8 @@ PX4FirmwarePlugin::PX4FirmwarePlugin(void)
         { PX4_CUSTOM_MAIN_MODE_RATTITUDE,   0,                                      true,   true,   true },
         { PX4_CUSTOM_MAIN_MODE_ALTCTL,      0,                                      true,   true,   true },
         { PX4_CUSTOM_MAIN_MODE_POSCTL,      0,                                      true,   true,   true },
-        { PX4_CUSTOM_MAIN_MODE_SIMPLE,      0,                                      true,   false,  true },
+        // simple can't be set by the user right now
+        { PX4_CUSTOM_MAIN_MODE_SIMPLE,      0,                                      false,   false,  true },
         { PX4_CUSTOM_MAIN_MODE_AUTO,        PX4_CUSTOM_SUB_MODE_AUTO_LOITER,        true,   true,   true },
         { PX4_CUSTOM_MAIN_MODE_AUTO,        PX4_CUSTOM_SUB_MODE_AUTO_MISSION,       true,   true,   true },
         { PX4_CUSTOM_MAIN_MODE_AUTO,        PX4_CUSTOM_SUB_MODE_AUTO_RTL,           true,   true,   true },
diff --git a/src/FirmwarePlugin/PX4/px4_custom_mode.h b/src/FirmwarePlugin/PX4/px4_custom_mode.h
index 6569ce6e0b092f6fb98b1804b77d9e98759ee4fc..2c0087e8f165189f89ec4d35015d7b45697fb38d 100644
--- a/src/FirmwarePlugin/PX4/px4_custom_mode.h
+++ b/src/FirmwarePlugin/PX4/px4_custom_mode.h
@@ -34,7 +34,7 @@
 /**
  * @file px4_custom_mode.h
  * PX4 custom flight modes
- *
+ * Copied from PX4 2017-07-08 - https://github.com/PX4/Firmware/blob/master/src/modules/commander/px4_custom_mode.h#L45
  */
 
 #ifndef PX4_CUSTOM_MODE_H_
@@ -50,8 +50,8 @@ enum PX4_CUSTOM_MAIN_MODE {
 	PX4_CUSTOM_MAIN_MODE_ACRO,
 	PX4_CUSTOM_MAIN_MODE_OFFBOARD,
 	PX4_CUSTOM_MAIN_MODE_STABILIZED,
-    PX4_CUSTOM_MAIN_MODE_RATTITUDE,
-    PX4_CUSTOM_MAIN_MODE_SIMPLE
+	PX4_CUSTOM_MAIN_MODE_RATTITUDE,
+	PX4_CUSTOM_MAIN_MODE_SIMPLE /* unused, but reserved for future use */
 };
 
 enum PX4_CUSTOM_SUB_MODE_AUTO {