diff --git a/setup_system.sh b/setup_system.sh
index 55c554c..98c3852 100755
--- a/setup_system.sh
+++ b/setup_system.sh
@@ -4,9 +4,8 @@
 # Default variables
 #
 
-UPGRADE_PACKAGES=false
-SCRIPT_NAME="$(basename -- "$0")"
-SCRIPT_DIR="$(
+upgrade_packages=false
+script_dir="$(
     cd -- "$(dirname "$0")" >/dev/null 2>&1 || exit 1
     pwd -P
 )"
@@ -16,7 +15,7 @@ SCRIPT_DIR="$(
 #
 
 function usage() {
-    echo "Usage: $SCRIPT_NAME [OPTIONS]"
+    echo "Usage: $(basename -- "$0") [OPTIONS]"
     echo
     echo "Options:"
     echo "  -h      Display help."
@@ -27,7 +26,7 @@ function usage() {
 while getopts ":uh" arg; do
     case $arg in
     h) usage ;;
-    u) UPGRADE_PACKAGES=true ;;
+    u) upgrade_packages=true ;;
     :)
         echo "$0: Must supply an argument to -$OPTARG." >&2
         exit 1
@@ -56,7 +55,7 @@ function is_laptop() {
 # Returns a comma-separated list of packages for one or more targets.
 # The packages file may contain multiple rows with the same target name.
 function get_packages() {
-    local pkg_file="$SCRIPT_DIR/.installer/packages"
+    local pkg_file="$script_dir/.installer/packages"
 
     for target in "$@"; do
         while read -r row; do
@@ -155,7 +154,7 @@ function setup_brew_formulas() {
 
     for package in $(get_packages "${targets[@]}"); do
         if brew list --full-name | grep -Eq "(^| )$package($| )" >/dev/null; then
-            if $UPGRADE_PACKAGES; then
+            if $upgrade_packages; then
                 echo "Package '$package' will be upgraded."
                 brew upgrade "$package" || return 2
             else
@@ -191,7 +190,7 @@ function setup_krew_plugins() {
 
     for package in $(get_packages "${targets[@]}"); do
         if kubectl-krew list | grep -q "^$package$" >/dev/null; then
-            if $UPGRADE_PACKAGES; then
+            if $upgrade_packages; then
                 echo "Package '$package' will be upgraded."
             else
                 echo "Package '$package' already exists."
@@ -246,7 +245,7 @@ function setup_arch_with_yay() {
 
     for package in $(get_packages "${targets[@]}"); do
         if pacman -Qs "^$package$" >/dev/null; then
-            if $UPGRADE_PACKAGES; then
+            if $upgrade_packages; then
                 echo "Package '$package' will be upgraded."
             else
                 echo "Package '$package' already exists."