diff --git a/ROMFS/px4fmu_common/init.d-posix/rcS b/ROMFS/px4fmu_common/init.d-posix/rcS
index a6e3988071..14c8d9a4c9 100644
--- a/ROMFS/px4fmu_common/init.d-posix/rcS
+++ b/ROMFS/px4fmu_common/init.d-posix/rcS
@@ -109,7 +109,9 @@ param set MAV_SYS_ID $((px4_instance+1))
 simulator_tcp_port=$((4560+px4_instance))
 udp_offboard_port_local=$((14580+px4_instance))
 udp_offboard_port_remote=$((14540+px4_instance))
-udp_gcs_port_local=$((14570+px4_instance))
+[ $px4_instance -gt 9 ] && udp_offboard_port_remote=14549 # use the same ports for more than 10 instances to avoid port overlaps
+udp_gcs_port_local=$((18570+px4_instance))
+
 
 if [ $AUTOCNF = yes ]
 then