diff --git a/sup b/sup
index 93bdf93..c4c544c 100755
--- a/sup
+++ b/sup
@@ -58,9 +58,7 @@ sup.scrot() {
 	[[ "$flag_scrot_fullscreen" ]] || { scrot_args+=( '-s' ); }
 	[[ "$cfg_scrot_delay" ]] && { scrot_args+=( "-d $cfg_scrot_delay" ); }
 
-	until [[ ! -e "${cfg_tmp_dir}/${tmp_file_name}" ]]; do
-		tmp_file_name="${RANDOM}${RANDOM}.${cfg_screenshot_ext}"
-	done
+	tmp_file_name="$(sup.mktemp "${cfg_tmp_dir}" "${cfg_screenshot_ext}")"
 
 	scrot "${scrot_args[@]}" "${cfg_tmp_dir}/$tmp_file_name" || {
 		sup.err "Failed to take a screenshot."
@@ -77,6 +75,21 @@ sup.exclude() {
 
 sup.if_url() { echo "$1" | grep -oE "$cfg_url_regex" &>/dev/null; }
 
+sup.mktemp() {
+	local tmp_file_name tmp_file_name_extra="$2" tmp_dir="$1" 
+
+	[[ -d "$tmp_dir" ]] || {
+		sup.err "${tmp_dir} does not exist or is not a directory."
+		return 1
+	}
+
+	until [[ ! -e "${tmp_dir}/${tmp_file_name}" ]]; do
+		tmp_file_name="${RANDOM}${RANDOM}${tmp_file_name_extra}"
+	done
+
+	echo "${tmp_dir}/${tmp_file_name}"
+}
+
 main() {
 	while [[ "$1" ]]; do
 		case "$1" in
@@ -104,7 +117,7 @@ main() {
 		target="${args[0]}"; [[ "$target" ]] || { sup.usage; exit 1; }
 
 		sup.if_url "$target" && {
-			file=`mktemp "$cfg_tmp_dir/sup_tmp_XXXXXX"`
+			file=`sup.mktemp "$cfg_tmp_dir"`
 
 			curl -s "$target" > "$file" || {
 				sup.err "Could not download file."