diff --git a/scanpix b/scanpix
index 02e9e12..41738ef 100755
--- a/scanpix
+++ b/scanpix
@@ -30,8 +30,8 @@
 ## VARIABLES
 
 # Default scan area in mm
-Y_SIZE="99" # width
-X_SIZE="151" # height
+Y_SIZE='99' # width
+X_SIZE='151' # height
 
 ## ARGUMENTS
 
@@ -39,9 +39,9 @@ if [ $# -gt 1 ]; then
 	echo "ERROR!  Too many arguments."
 	exit 2
 elif [ $# -eq 1 ]; then
-	DIR="$1"
+	DIR="${1}"
 else
-	DIR="$PWD"
+	DIR="${PWD}"
 fi
 
 
@@ -56,7 +56,7 @@ if [ "${SCANNER}" == "" ]; then
 	exit 3
 fi
 echo "found."
-echo "Using scanner: $SCANNER"
+echo "Using scanner: ${SCANNER}"
 
 # Ask user for a directory to scan into
 DIR=$(zenity --entry --title="Scan Location" \
@@ -66,18 +66,18 @@ DIR=$(zenity --entry --title="Scan Location" \
 # User didn't enter a valid directory
 if [ ! -d "${DIR}" ]; then
 	zenity --error --title="Error: Scan location not found" \
-		--text="Couldn't find $DIR.  Try again (no trailing slashes)"
+		--text="Couldn't find ${DIR}.  Try again (no trailing slashes)"
 	exit 1
-else echo "Saving photos to $DIR"; fi
+else echo "Saving photos to ${DIR}"; fi
 
 # Ask for photo size
 Y_SIZE=$(zenity --entry --title="Photo width" \
 	--text="How wide are the photos (in mm)?" \
-	--entry-text="$Y_SIZE")
+	--entry-text="${Y_SIZE}")
 X_SIZE=$(zenity --entry --title="Photo height" \
 	--text="How high are the photos (in mm)?" \
-	--entry-text="$X_SIZE")
-echo "Scanning photos at $X_SIZE x $Y_SIZE"
+	--entry-text="${X_SIZE}")
+echo "Scanning photos at ${X_SIZE} x ${Y_SIZE}"
 
 # Wait for first photo to be placed
 if ! zenity --question --title="Prepare scan" \
@@ -110,7 +110,7 @@ while true; do
 		else echo "Done."
 			# Scan again?
 			if ! zenity --question --title="Scan Completed" \
-				--text="Photo scanned to $NOW.jpg\nNow what? " \
+				--text="Photo scanned to ${NOW}.jpg\nNow what? " \
 				--ok-label="Scan another" --cancel-label="Quit"
 			then exit 0; fi
 		fi