diff --git a/src/cmdlib.sh b/src/cmdlib.sh
index f23275ff99..fbf78b064b 100755
--- a/src/cmdlib.sh
+++ b/src/cmdlib.sh
@@ -172,10 +172,13 @@ prepare_build() {
     if ! [ -d builds ]; then
         fatal "No $(pwd)/builds found; did you run coreos-assembler init?"
     elif ! has_privileges; then
-        if [ ! -f cache/cache.qcow2 ]; then
-            qemu-img create -f qcow2 cache/cache.qcow2 10G
-            LIBGUESTFS_BACKEND=direct virt-format --filesystem=xfs -a cache/cache.qcow2
+        # "cache2" has an explicit label so we can find it in qemu easily
+        if [ ! -f cache/cache2.qcow2 ]; then
+            qemu-img create -f qcow2 cache/cache2.qcow2 10G
+            LIBGUESTFS_BACKEND=direct virt-format --filesystem=xfs --label=cosa-cache -a cache/cache2.qcow2
         fi
+        # And remove the old one
+        rm -vf cache/cache.qcow2
     fi
 
     workdir="$(pwd)"
@@ -471,7 +474,7 @@ $(cat "${DIR}"/supermin-init-prelude.sh)
 rc=0
 sh ${TMPDIR}/cmd.sh || rc=\$?
 echo \$rc > ${workdir}/tmp/rc
-if [ -b /dev/sdb1 ]; then
+if [ -n "\${cachedev}" ]; then
     /sbin/fstrim -v ${workdir}/cache
 fi
 /sbin/reboot -f
@@ -483,8 +486,8 @@ EOF
     echo "$@" > "${TMPDIR}"/cmd.sh
 
     cachedisk=()
-    if [ -f "${workdir}/cache/cache.qcow2" ]; then
-        cachedisk=("-drive" "if=none,id=drive-scsi0-0-0-1,discard=unmap,file=${workdir}/cache/cache.qcow2" \
+    if [ -f "${workdir}/cache/cache2.qcow2" ]; then
+        cachedisk=("-drive" "if=none,id=drive-scsi0-0-0-1,discard=unmap,file=${workdir}/cache/cache2.qcow2" \
                    "-device" "scsi-hd,bus=scsi0.0,channel=0,scsi-id=0,lun=1,drive=drive-scsi0-0-0-1,id=scsi0-0-0-1")
     fi
 
diff --git a/src/supermin-init-prelude.sh b/src/supermin-init-prelude.sh
index a84209a415..8b2eb78088 100644
--- a/src/supermin-init-prelude.sh
+++ b/src/supermin-init-prelude.sh
@@ -30,8 +30,11 @@ if [ -L "${workdir}"/src/config ]; then
     mount -t 9p -o rw,trans=virtio,version=9p2000.L source "${workdir}"/src/config
 fi
 mkdir -p "${workdir}"/cache /host/container-work
-if [ -b /dev/sdb1 ]; then
-    mount /dev/sdb1 "${workdir}"/cache
+cachedev=$(blkid -lt LABEL=cosa-cache -o device)
+if [ -n "${cachedev}" ]; then
+    mount "${cachedev}" "${workdir}"/cache
+else
+    echo "No cosa-cache filesystem found!"
 fi
 
 if [ -f "${workdir}/tmp/supermin/supermin.env" ]; then