diff --git a/btrfs-snapshots.sh b/btrfs-snapshots.sh
index 0dff4a4..2a2c9e5 100755
--- a/btrfs-snapshots.sh
+++ b/btrfs-snapshots.sh
@@ -148,9 +148,9 @@ for fs in ${BTRFS_VOLUMES}; do
         sudo umount "$TMP_MNT"
         if test $fast -eq 0; then
             echo "Defragment subvolume: '${fs}'"
-            sudo btrfs filesystem defragment ${fs}
+            sudo btrfs filesystem defragment "${fs}"
             echo "Rebalance subvolume: '${fs}'"
-            sudo btrfs balance start ${fs}
+            sudo btrfs balance start "${fs}"
         fi
     else
         echo "ERROR: no device found for $fs" 1>&2