diff --git a/mkosi.images/system/mkosi.conf b/mkosi.images/system/mkosi.conf
index f8a91df5ec..bf08e756e2 100644
--- a/mkosi.images/system/mkosi.conf
+++ b/mkosi.images/system/mkosi.conf
@@ -15,6 +15,9 @@ ExtraTrees=
 
 PostInstallationScripts=mkosi.sanitizers.chroot
 
+Environment=
+        SYSTEMD_REPART_OVERRIDE_FSTYPE_ROOT=%F
+
 InitrdPackages=
         btrfs-progs
         findutils
diff --git a/mkosi.images/system/mkosi.conf.d/10-centos/mkosi.conf b/mkosi.images/system/mkosi.conf.d/10-centos/mkosi.conf
index 25059c2292..121257e8e5 100644
--- a/mkosi.images/system/mkosi.conf.d/10-centos/mkosi.conf
+++ b/mkosi.images/system/mkosi.conf.d/10-centos/mkosi.conf
@@ -5,9 +5,14 @@ Distribution=centos
 
 [Content]
 Environment=
-        # The kernel versions in CentOS Stream 9 doesn't support orphan_file, but later versions of
-        # mkfs.ext4 enabled it by default, so we disable it explicitly.
-        Environment=SYSTEMD_REPART_MKFS_OPTIONS_EXT4="-O ^orphan_file"
+        Environment=
+                # We'd prefer to use XFS here but it fails to mount on duplicate filesystem UUIDs which
+                # happens when running tests in parallel so we use ext4 instead.
+                SYSTEMD_REPART_OVERRIDE_FSTYPE_ROOT=ext4
+                # The kernel versions in CentOS Stream 9 doesn't support orphan_file, but later versions of
+                # mkfs.ext4 enabled it by default, so we disable it explicitly.
+                SYSTEMD_REPART_MKFS_OPTIONS_EXT4="-O ^orphan_file"
+
         GIT_URL=https://git.centos.org/rpms/systemd.git
         GIT_BRANCH=c9s-sig-hyperscale
         GIT_COMMIT=8cf2aed0181920611421384f7374720db269d6c7
diff --git a/mkosi.images/system/mkosi.repart/10-root.conf b/mkosi.images/system/mkosi.repart/10-root.conf
index 3c25dbfb14..c774086fb4 100644
--- a/mkosi.images/system/mkosi.repart/10-root.conf
+++ b/mkosi.images/system/mkosi.repart/10-root.conf
@@ -2,7 +2,6 @@
 
 [Partition]
 Type=root
-Format=btrfs
 CopyFiles=/
 SizeMinBytes=8G
 SizeMaxBytes=8G