diff --git a/ROMFS/px4fmu_common/init.d-posix/airframes/CMakeLists.txt b/ROMFS/px4fmu_common/init.d-posix/airframes/CMakeLists.txt
index d54134e437..743d54fc70 100644
--- a/ROMFS/px4fmu_common/init.d-posix/airframes/CMakeLists.txt
+++ b/ROMFS/px4fmu_common/init.d-posix/airframes/CMakeLists.txt
@@ -94,4 +94,6 @@ px4_add_romfs_files(
 
 	17001_flightgear_tf-g1
 	17002_flightgear_tf-g2
+
+	# [22000, 22999] Reserve for custom models
 )