diff --git a/ROMFS/px4fmu_common/init.d-posix/rcS b/ROMFS/px4fmu_common/init.d-posix/rcS
index 43630694bb..1bcdf974fe 100644
--- a/ROMFS/px4fmu_common/init.d-posix/rcS
+++ b/ROMFS/px4fmu_common/init.d-posix/rcS
@@ -260,13 +260,19 @@ fi
 navigator start
 
 # Try to start the microdds_client with UDP transport if module exists
-if [ $px4_instance -eq 0 ]
+microdds_ns=""
+if [ "$px4_instance" -ne "0" ]
 then
-	microdds_client start -t udp -p 8888
-else
+	# Assign new xrce dds key based on instance number and set default namespace
 	param set XRCE_DDS_KEY ${px4_instance}
-	microdds_client start -t udp -p 8888 -n "px4_$px4_instance"
+	microdds_ns="-n px4_$px4_instance"
 fi
+if [ -n "$PX4_MICRODDS_NS" ]
+then
+	# Override namespace if environment variable is defined
+	microdds_ns="-n $PX4_MICRODDS_NS"
+fi
+microdds_client start -t udp -p 8888 $microdds_ns
 
 if param greater -s MNT_MODE_IN -1
 then