diff --git a/tools/deploy/spritename.ts b/tools/deploy/spritename.ts
index 6f8e35bb..936846bc 100644
--- a/tools/deploy/spritename.ts
+++ b/tools/deploy/spritename.ts
@@ -1,14 +1,14 @@
 
-export type SpriteName = {id : number | string, extra : [string, string][]};
+export type SpriteName = {id : number | string, extra : Map<string, string>};
 
 export function parse(s : string) : SpriteName {
     const parts = s.split("-");
     const id = parts[0].match(/^[0-9]+$/) ? parseInt(parts[0], 10) : parts[0];
-    const extra : [string, string][] = [];
+    const extra = new Map<string, string>();
     for (const part of parts.slice(1)) {
         if (part.length === 0)
             throw new Error(`Can't parse ${s}`);
-        extra.push([part[0], part.slice(1)]);
+        extra.set(part[0], part.slice(1));
     }
     return {id, extra};
 }
@@ -16,11 +16,9 @@ export function parse(s : string) : SpriteName {
 export function format(si : SpriteName) {
     let s = si.id.toString();
     const extra = [];
-    for (const [k, v] of si.extra) {
+    for (const [k, v] of si.extra.entries()) {
         extra.push(`-${k}${v}`);
     }
     extra.sort();
     return s + extra.join('');
 }
-
-// TODO: update()?