diff --git a/mkosi.extra/usr/lib/repart.d/40-root.conf b/mkosi.extra/usr/lib/repart.d/40-root.conf
index cca623a1..188fc5ba 100644
--- a/mkosi.extra/usr/lib/repart.d/40-root.conf
+++ b/mkosi.extra/usr/lib/repart.d/40-root.conf
@@ -4,6 +4,7 @@
 Type=root
 Format=btrfs
 SizeMinBytes=1G
+SizeMaxBytes=40G
 Weight=20000
 Subvolumes=/var
 MakeDirectories=/var/log/journal