diff --git a/update.sh b/update.sh
index bbbbec1..9de9012 100755
--- a/update.sh
+++ b/update.sh
@@ -7,69 +7,69 @@ openntpd_version=`cat VERSION`
 # pull in latest upstream code
 echo "pulling upstream openbsd source"
 if [ ! -d openbsd ]; then
-	if [ -z "$OPENNTPD_GIT" ]; then
+	if [ -z "${OPENNTPD_GIT}" ]; then
 		git clone https://github.com/openntpd-portable/openntpd-openbsd.git openbsd
 	else
-		git clone $OPENNTPD_GIT/openbsd
+		git clone "${OPENNTPD_GIT}/openbsd"
 	fi
 fi
 (cd openbsd
  git fetch
- git checkout $openbsd_branch
+ git checkout "${openbsd_branch}"
  git pull --rebase)
 
 # setup source paths
 dir=`pwd`
-patches=$dir/patches
-etc_src=$dir/openbsd/src/etc
-libc_inc=$dir/openbsd/src/include
-libc_src=$dir/openbsd/src/lib/libc
-arc4random_src=$dir/openbsd/src/lib/libcrypto/arc4random
-libutil_src=$dir/openbsd/src/lib/libutil
-ntpd_src=$dir/openbsd/src/usr.sbin/ntpd
+patches="${dir}/patches"
+etc_src="${dir}/openbsd/src/etc"
+libc_inc="${dir}/openbsd/src/include"
+libc_src="${dir}/openbsd/src/lib/libc"
+arc4random_src="${dir}/openbsd/src/lib/libcrypto/arc4random"
+libutil_src="${dir}/openbsd/src/lib/libutil"
+ntpd_src="${dir}/openbsd/src/usr.sbin/ntpd"
 
 do_cp_libc() {
-	sed "/DEF_WEAK/d" < "$1" > "$2"/`basename "$1"`
+	sed "/DEF_WEAK/d" < "${1}" > "${2}"/`basename "${1}"`
 }
 CP_LIBC='do_cp_libc'
 CP='cp -p'
 PATCH='patch -p0 -s'
 
-$CP $etc_src/ntpd.conf ./
-sed '/DECLS/d' $libc_inc/md5.h > include/md5.h
-sed '/DECLS/d' $libc_inc/sha2.h > include/sha2_openbsd.h
-$CP $libutil_src/imsg.h include/
-$CP $libutil_src/imsg.c compat/
-$CP $libutil_src/imsg-buffer.c compat/
-(cd compat; $PATCH < $patches/patch-imsg.c)
+${CP} "${etc_src}/ntpd.conf" ./
+sed '/DECLS/d' "${libc_inc}/md5.h" > include/md5.h
+sed '/DECLS/d' "${libc_inc}/sha2.h" > include/sha2_openbsd.h
+${CP} "${libutil_src}/imsg.h" include/
+${CP} "${libutil_src}/imsg.c" compat/
+${CP} "${libutil_src}/imsg-buffer.c" compat/
+(cd compat; ${PATCH} < "${patches}/patch-imsg.c")
 
 for i in explicit_bzero.c strlcpy.c strlcat.c; do
-	$CP_LIBC $libc_src/string/$i compat
+	${CP_LIBC} "${libc_src}/string/${i}" compat
 done
-$CP_LIBC $libc_src/stdlib/reallocarray.c compat
-$CP_LIBC $libc_src/stdlib/recallocarray.c compat
-$CP_LIBC $libc_src/stdlib/strtonum.c compat
-$CP_LIBC $libc_src/crypt/arc4random.c compat
-$CP_LIBC $libc_src/crypt/arc4random_uniform.c compat
-$CP_LIBC $libc_src/crypt/chacha_private.h compat
-$CP_LIBC $libc_src/hash/md5.c compat
-$CP_LIBC $libc_src/hash/sha2.c compat
-for i in $arc4random_src/getentropy_*.c; do
-	sed -e 's/openssl\/sha.h/sha2.h/' < $i > compat/`basename $i`
+${CP_LIBC} "${libc_src}/stdlib/reallocarray.c" compat
+${CP_LIBC} "${libc_src}/stdlib/recallocarray.c" compat
+${CP_LIBC} "${libc_src}/stdlib/strtonum.c" compat
+${CP_LIBC} "${libc_src}/crypt/arc4random.c" compat
+${CP_LIBC} "${libc_src}/crypt/arc4random_uniform.c" compat
+${CP_LIBC} "${libc_src}/crypt/chacha_private.h" compat
+${CP_LIBC} "${libc_src}/hash/md5.c" compat
+${CP_LIBC} "${libc_src}/hash/sha2.c" compat
+for i in "${arc4random_src}"/getentropy_*.c; do
+	sed -e 's/openssl\/sha.h/sha2.h/' < "${i}" > compat/`basename "${i}"`
 done
-$CP $arc4random_src/arc4random_*.h compat
+${CP} "${arc4random_src}"/arc4random_*.h compat
 
 for i in client.c config.c constraint.c control.c log.c ntp.c ntp.h \
 	ntp_dns.c ntp_msg.c ntpd.c ntpd.h parse.y sensors.c server.c util.c \
 	ntpctl.8 ntpd.8 ntpd.conf.5 ; do
-	file=`basename $i`
-	echo Copying $file
-	$CP $ntpd_src/$i src
+	file=`basename ${i}`
+	echo Copying ${file}
+	${CP} "${ntpd_src}/${i}" src
 done
 
 (cd src
 for i in ../patches/*.patch; do
-	echo Patching $i
-	$PATCH -p4 < $i
+	echo Patching ${i}
+	${PATCH} -p4 < "${i}"
 done
 )