diff --git a/games/factorio_manager.sh b/games/factorio_manager.sh
index 92365e61bf8ac0f0b4be422413b7248eeef9b8dc..df505686f2ed1f54712b191eeb17a7425e581d5b 100755
--- a/games/factorio_manager.sh
+++ b/games/factorio_manager.sh
@@ -234,7 +234,7 @@ EOF
 # Set-up colours for message printing if we're not piping and terminal is
 # capable of outputting the colors.
 _color_terminal=$(tput colors 2>&1)
-if [[ -t 1 ]] && (( ${_color_terminal} > 0 )); then
+if [[ -t 1 ]] && (( _color_terminal > 0 )); then
     _text_black=$(tput setaf 0)
     _text_red=$(tput setaf 1)
     _text_green=$(tput setaf 2)
@@ -1075,7 +1075,7 @@ function select_factorio_version() {
         read -r -e -p "Please specify what version you would like to use (enter for $default_marker): " selected_option
         [[ -z $selected_option ]] && selected_option="$default_option"
 
-        if [[ $selected_option =~ ^[[:digit:]]+$ ]] && (( $selected_option >= 1 && $selected_option <= ${#game_versions_available[@]} )); then
+        if [[ $selected_option =~ ^[[:digit:]]+$ ]] && (( selected_option >= 1 && selected_option <= ${#game_versions_available[@]} )); then
             game_version_selected="${game_versions_available[$selected_option-1]}"
         else
             error "Invalid option selected, please try again."
@@ -1179,7 +1179,7 @@ while getopts "qdvh" opt; do
     esac
 done
 i=$OPTIND
-shift $(($i-1))
+shift $((i-1))
 
 # Make sure the manager home directory exists.
 if [[ ! -e $manager_directory ]]; then
@@ -1218,7 +1218,7 @@ if [[ $command == set-game-dir ]]; then
         fi
     done
 
-    if (( $factorio_versions_found == 0 )); then
+    if (( factorio_versions_found == 0 )); then
         error "Could not locate any Factorio installations under: $game_installations_directory_target"
 
         exit "$ERROR_GENERAL"