diff --git a/src/db.ts b/src/db.ts
index bc84de95..bff1190f 100644
--- a/src/db.ts
+++ b/src/db.ts
@@ -4,7 +4,7 @@ const kv = await Deno.openKv();
 
 const userSchema = z.object({
   pubkey: z.string().regex(/^[0-9a-f]{64}$/).describe('primary'),
-  username: z.string().regex(/^[\w_]+$/).describe('unique'),
+  username: z.string().regex(/^[\w_]{1,30}$/).describe('unique'),
   createdAt: z.date(),
 });