diff --git a/mkosi.images/system/mkosi.conf.d/10-debian-ubuntu/mkosi.build.chroot b/mkosi.images/system/mkosi.conf.d/10-debian-ubuntu/mkosi.build.chroot
index 106b8ed4e6..e5224b8728 100755
--- a/mkosi.images/system/mkosi.conf.d/10-debian-ubuntu/mkosi.build.chroot
+++ b/mkosi.images/system/mkosi.conf.d/10-debian-ubuntu/mkosi.build.chroot
@@ -28,7 +28,7 @@ fi
 # Add a new changelog entry to update the version. We use a fixed date since a dynamic one causes a full
 # rebuild every time.
 cat >debian/changelog.new <<EOF
-systemd ($(cat meson.version).$(date "+%Y%m%d%H%M%S" --date "@$TS")) UNRELEASED; urgency=low
+systemd ($(cat meson.version)-$(date "+%Y%m%d%H%M%S" --date "@$TS")) UNRELEASED; urgency=low
 
   * Automatic build from mkosi