diff --git a/etc/MAKEDEV b/etc/MAKEDEV
index 27e54bafe4f2..2fcc44179777 100644
--- a/etc/MAKEDEV
+++ b/etc/MAKEDEV
@@ -724,7 +724,7 @@ acd*|cd*|mcd*|scd*)
 	mcd*) units=`expr $i : '...\(.*\)'`; name=mcd; blk=7; chr=29;;
 	scd*) units=`expr $i : '...\(.*\)'`; name=scd; blk=16; chr=45;;
 	esac
-	if [ -z "${units}" -o ${units} -le 0 ]; then
+	if [ -z "${units}" -o "${units}" -le 0 ]; then
 		units=1
 	fi
 	if [ "${units}" -le 31 ]; then
diff --git a/etc/etc.alpha/MAKEDEV b/etc/etc.alpha/MAKEDEV
index 24b23ca1fb4e..c5010e305cc5 100644
--- a/etc/etc.alpha/MAKEDEV
+++ b/etc/etc.alpha/MAKEDEV
@@ -694,7 +694,7 @@ acd*|cd*|mcd*|scd*)
 	mcd*) units=`expr $i : '...\(.*\)'`; name=mcd; blk=7; chr=29;;
 	scd*) units=`expr $i : '...\(.*\)'`; name=scd; blk=16; chr=45;;
 	esac
-	if [ -z "${units}" -o ${units} -le 0 ]; then
+	if [ -z "${units}" -o "${units}" -le 0 ]; then
 		units=1
 	fi
 	if [ "${units}" -le 31 ]; then
diff --git a/etc/etc.i386/MAKEDEV b/etc/etc.i386/MAKEDEV
index 27e54bafe4f2..2fcc44179777 100644
--- a/etc/etc.i386/MAKEDEV
+++ b/etc/etc.i386/MAKEDEV
@@ -724,7 +724,7 @@ acd*|cd*|mcd*|scd*)
 	mcd*) units=`expr $i : '...\(.*\)'`; name=mcd; blk=7; chr=29;;
 	scd*) units=`expr $i : '...\(.*\)'`; name=scd; blk=16; chr=45;;
 	esac
-	if [ -z "${units}" -o ${units} -le 0 ]; then
+	if [ -z "${units}" -o "${units}" -le 0 ]; then
 		units=1
 	fi
 	if [ "${units}" -le 31 ]; then