diff --git a/framework/framework/api.ts b/framework/framework/api.ts
index a7086f8ed..7da2e5f36 100644
--- a/framework/framework/api.ts
+++ b/framework/framework/api.ts
@@ -190,7 +190,7 @@ export class ApiHandler<C extends Context> extends Handler<C> {
         if (!['get', 'post'].includes(this.request.method.toLowerCase())) {
             throw new MethodNotAllowedError(this.request.method);
         }
-        if (!APIS[op]) throw new BadRequestError('Invalid operation');
+        if (!APIS[op]) throw new BadRequestError(`Invalid API operation: ${op}`);
         if (APIS[op].type === 'Subscription') {
             throw new BadRequestError('Subscription operation cannot be called in HTTP handler');
         }
@@ -226,7 +226,7 @@ export class ApiConnectionHandler<C extends Context> extends ConnectionHandler<C
             this.isRpc = true;
             return;
         }
-        if (!APIS[op]) throw new BadRequestError('Invalid operation');
+        if (!APIS[op]) throw new BadRequestError(`Invalid API operation: ${op}`);
         if (APIS[op].type !== 'Subscription') {
             throw new BadRequestError('Only subscription operations are supported');
         }
@@ -250,7 +250,7 @@ export class ApiConnectionHandler<C extends Context> extends ConnectionHandler<C
                 throw new BadRequestError('Invalid message');
             }
         }
-        if (!APIS[message.op]) throw new BadRequestError('Invalid operation');
+        if (!APIS[message.op]) throw new BadRequestError(`Invalid API operation: ${message.op}`);
         if (APIS[message.op].type !== 'Subscription') {
             throw new BadRequestError('Only subscription operations are supported');
         }
diff --git a/framework/framework/package.json b/framework/framework/package.json
index cb9cdb6df..b24c44d34 100644
--- a/framework/framework/package.json
+++ b/framework/framework/package.json
@@ -1,6 +1,6 @@
 {
     "name": "@hydrooj/framework",
-    "version": "0.2.4",
+    "version": "0.2.5",
     "main": "index.ts",
     "license": "MIT",
     "repository": "https://github.com/hydro-dev/Hydro",
@@ -13,7 +13,7 @@
         "@mongodb-js/saslprep": "^1.3.2",
         "emoji-regex": "^10.6.0",
         "fs-extra": "^11.3.2",
-        "koa": "^3.0.3",
+        "koa": "^3.1.1",
         "koa-body": "^7.0.0",
         "koa-compress": "^5.1.1",
         "path-to-regexp": "^8.3.0",
diff --git a/framework/framework/server.ts b/framework/framework/server.ts
index 8fea33d18..dc12c8a8e 100644
--- a/framework/framework/server.ts
+++ b/framework/framework/server.ts
@@ -412,6 +412,8 @@ ${c.response.status} ${endTime - startTime}ms ${c.response.length}`);
                 formLimit: '8mb',
                 formidable: {
                     uploadDir,
+                    allowEmptyFiles: true,
+                    minFileSize: 0,
                     maxFileSize: parseMemoryMB(this.config.upload) * 1024 * 1024,
                     keepExtensions: true,
                 },