diff --git a/ROMFS/px4fmu_common/init.d/rcS b/ROMFS/px4fmu_common/init.d/rcS
index 36a5124415..2c9387ff06 100644
--- a/ROMFS/px4fmu_common/init.d/rcS
+++ b/ROMFS/px4fmu_common/init.d/rcS
@@ -230,6 +230,7 @@ then
 				tone_alarm $TUNE_ERR
 			fi
 		fi
+		unset IO_FILE
 
 		if [ $IO_PRESENT == no ]
 		then