diff --git a/qa/workunits/cephtool/test.sh b/qa/workunits/cephtool/test.sh
index 6ee0e5aec29..13690af4b5d 100755
--- a/qa/workunits/cephtool/test.sh
+++ b/qa/workunits/cephtool/test.sh
@@ -1028,6 +1028,8 @@ function test_mon_mds()
   ceph fs new $FS_NAME fs_metadata mds-ec-pool --force 2>$TMPFILE
   check_response 'erasure-code' $? 22
   ceph fs new $FS_NAME mds-ec-pool fs_data 2>$TMPFILE
+  check_response 'already used by filesystem' $? 22
+  ceph fs new $FS_NAME mds-ec-pool fs_data --force 2>$TMPFILE
   check_response 'erasure-code' $? 22
   ceph fs new $FS_NAME mds-ec-pool mds-ec-pool 2>$TMPFILE
   check_response 'erasure-code' $? 22
@@ -1067,8 +1069,12 @@ function test_mon_mds()
   ceph fs new $FS_NAME fs_metadata mds-tier --force 2>$TMPFILE
   check_response 'in use as a cache tier' $? 22
   ceph fs new $FS_NAME mds-tier fs_data 2>$TMPFILE
+  check_response 'already used by filesystem' $? 22
+  ceph fs new $FS_NAME mds-tier fs_data --force 2>$TMPFILE
   check_response 'in use as a cache tier' $? 22
   ceph fs new $FS_NAME mds-tier mds-tier 2>$TMPFILE
+  check_response 'already used by filesystem' $? 22
+  ceph fs new $FS_NAME mds-tier mds-tier --force 2>$TMPFILE
   check_response 'in use as a cache tier' $? 22
   set -e
 
@@ -1099,6 +1105,8 @@ function test_mon_mds()
   # ...but not as the metadata pool
   set +e
   ceph fs new $FS_NAME mds-ec-pool fs_data 2>$TMPFILE
+  check_response 'already used by filesystem' $? 22
+  ceph fs new $FS_NAME mds-ec-pool fs_data --force 2>$TMPFILE
   check_response 'erasure-code' $? 22
   set -e