diff --git a/backup.sh b/backup.sh
index 7447daa..23b66f0 100755
--- a/backup.sh
+++ b/backup.sh
@@ -45,7 +45,7 @@ run_send_recv()
 {
     ssh_cmd="ssh $SSH_SEND_OPTS -o port=$port $user@$addr"
     pv_cmd="pv -qL ${speed:-$DEFAULT_SPEED}"
-    if [ $ZB_TEST_MODE = "TRUE" ]; then
+    if ["$ZB_TEST_MODE" = "TRUE" ]; then
         echo "$send_cmd | $pv_cmd | $ssh_cmd $recv_cmd"
     else
         $send_cmd | $pv_cmd | $ssh_cmd $recv_cmd
@@ -54,7 +54,7 @@ run_send_recv()
 
 run_snapshot()
 {
-    if [ $ZB_TEST_MODE = "TRUE" ]; then
+    if [ "$ZB_TEST_MODE" = "TRUE" ]; then
         echo zfs snapshot $ZFS_SNAPSHOT_OPTS $dset@$snapid
     else
         zfs snapshot $ZFS_SNAPSHOT_OPTS $dset@$snapid
@@ -63,7 +63,7 @@ run_snapshot()
 
 run_allow()
 {
-    if [ $ZB_TEST_MODE = "TRUE" ]; then
+    if [ "$ZB_TEST_MODE" = "TRUE" ]; then
         echo zfs allow -u $LOCAL_USER $ORIGIN_PERMS $dset
     else
         zfs allow -u $LOCAL_USER $ORIGIN_PERMS $dset
@@ -73,7 +73,7 @@ run_allow()
 run_remote()
 {
     ssh_cmd="ssh $SSH_SEND_OPTS -o port=$port $user@$addr"
-    if [ $ZB_TEST_MODE = "TRUE" ]; then
+    if [ "$ZB_TEST_MODE" = "TRUE" ]; then
         echo "\`$ssh_cmd $remote_cmd\`"
     else
         $ssh_cmd $remote_cmd
@@ -81,7 +81,7 @@ run_remote()
 }
 
 set_compression() {
-    case $SEND_COMPRESSED in
+    case "$SEND_COMPRESSED" in
         [tTyY]*) ZFS_SEND_OPTS="$ZFS_SEND_OPTS -c"
         debug "Enabled send as compressed datasets." ;;
     esac
@@ -90,14 +90,14 @@ set_compression() {
 populate_datasets()
 {
     while read dset dataset_options; do
-        case $dset in
+        case "$dset" in
             \#*) continue;;
         esac
 
         snapshot_dataset="yes"
         send_dataset="yes"
         for option in $dataset_options; do
-            case $option in
+            case "$option" in
                 "nosnap"*    )
                     snapshot_dataset=""
                     ;;
@@ -133,8 +133,8 @@ list_datasets()
 list_remote_datasets() {
     while read addr user port zroot speed; do
         echo "=== $user@$addr $zroot ==="
-        if [ $zroot ]; then
-            case $zroot in
+        if [ "$zroot" ]; then
+            case "$zroot" in
                 *"/") ;;
                 *) zroot="$zroot/" ;;
             esac
@@ -157,7 +157,7 @@ get_latest_snapshot()
 get_latest_remote_snapshot()
 {
     if [ $zroot ]; then
-        case $zroot in
+        case "$zroot" in
             *"/") ;;
             *) zroot="$zroot/" ;;
         esac
@@ -179,8 +179,8 @@ zfs_allow_mirrors()
 {
     while read addr user port zroot speed; do
         echo "=== $user@$addr $zroot ==="
-        if [ $zroot ]; then
-            case $zroot in
+        if [ "$zroot" ]; then
+            case "$zroot" in
                 *"/") ;;
                 *) zroot="$zroot/" ;;
             esac
@@ -200,7 +200,7 @@ create_snapshots()
     snapid="`date -I`-`date +%s`-$LOCAL_TZ"
     for dset in $SNAPSHOT_DATASETS; do
         run_snapshot
-        debug Created snapshot $dset@$snapid.
+        debug "Created snapshot $dset@$snapid."
     done
 }
 
@@ -208,8 +208,8 @@ send_latest()
 {
     while read addr user port zroot speed; do
         echo "=== $user@$addr $zroot ==="
-        if [ $zroot ]; then
-            case $zroot in
+        if [ "$zroot" ]; then
+            case "$zroot" in
                 *"/") ;;
                 *) zroot="$zroot/" ;;
             esac
@@ -230,8 +230,8 @@ send_increment()
 {
     while read addr user port zroot speed; do
         echo "=== $user@$addr $zroot ==="
-        if [ $zroot ]; then
-            case $zroot in
+        if [ "$zroot" ]; then
+            case "$zroot" in
                 *"/") ;;
                 *) zroot="$zroot/" ;;
             esac