diff --git a/tests/common b/tests/common
index 55ef442f..860bc472 100644
--- a/tests/common
+++ b/tests/common
@@ -308,7 +308,7 @@ check_prereq()
 
 check_global_prereq()
 {
-	which $1 &> /dev/null
+	which "$1" &> /dev/null
 	if [ $? -ne 0 ]; then
 		_fail "Failed system wide prerequisities: $1";
 	fi
@@ -659,11 +659,11 @@ setup_loopdevs()
 prepare_loopdevs()
 {
 	for i in `seq $nloopdevs`; do
-		touch $loopdev_prefix$i
-		chmod a+rw $loopdev_prefix$i
-		truncate -s0 $loopdev_prefix$i
-		truncate -s2g $loopdev_prefix$i
-		loopdevs[$i]=`run_check_stdout $SUDO_HELPER losetup --find --show $loopdev_prefix$i`
+		touch "$loopdev_prefix$i"
+		chmod a+rw "$loopdev_prefix$i"
+		truncate -s0 "$loopdev_prefix$i"
+		truncate -s2g "$loopdev_prefix$i"
+		loopdevs[$i]=`run_check_stdout $SUDO_HELPER losetup --find --show "$loopdev_prefix$i"`
 	done
 }
 
@@ -671,10 +671,10 @@ prepare_loopdevs()
 cleanup_loopdevs()
 {
 	for dev in ${loopdevs[@]}; do
-		run_check $SUDO_HELPER losetup -d $dev
+		run_check $SUDO_HELPER losetup -d "$dev"
 	done
 	for i in `seq $nloopdevs`; do
-		truncate -s0 $loopdev_prefix$i
+		truncate -s0 "$loopdev_prefix$i"
 		rm -- "$loopdev_prefix$i"
 	done
 	run_check $SUDO_HELPER losetup --all
@@ -686,7 +686,7 @@ init_env()
 	export TEST_MNT
 	mkdir -p "$TEST_MNT" || { echo "Failed mkdir -p $TEST_MNT"; exit 1; }
 
-	source $TEST_TOP/common.local
+	source "$TEST_TOP/common.local"
 
 	if [ "$TEST_ENABLE_OVERRIDE" = 'true' -a -n "$RESULTS" ]; then
 		echo "INCLUDE common.local" >> "$RESULTS"