diff --git a/packages/backend/package.json b/packages/backend/package.json
index f775a99a5..87712faf7 100644
--- a/packages/backend/package.json
+++ b/packages/backend/package.json
@@ -19,7 +19,7 @@
 		"@elastic/elasticsearch": "7.11.0",
 		"@koa/cors": "3.1.0",
 		"@koa/multer": "3.0.0",
-		"@koa/router": "10.1.1",
+		"@koa/router": "9.0.1",
 		"@sinonjs/fake-timers": "9.1.1",
 		"@syuilo/aiscript": "0.11.1",
 		"@types/bcryptjs": "2.4.2",
diff --git a/packages/backend/yarn.lock b/packages/backend/yarn.lock
index c5b123772..67a02742d 100644
--- a/packages/backend/yarn.lock
+++ b/packages/backend/yarn.lock
@@ -128,10 +128,10 @@
   resolved "https://registry.yarnpkg.com/@koa/multer/-/multer-3.0.0.tgz#439777949f28097d7b329c0b4ce3048074c862f8"
   integrity sha512-y+OQBmex5D1jIl723gAEUYcAWPEicIXppaAKw/zCMfpllQ08ZNweDPwoCLxEoatqd5pCu2XG6V8dl67JRq3RJw==
 
-"@koa/router@10.1.1":
-  version "10.1.1"
-  resolved "https://registry.yarnpkg.com/@koa/router/-/router-10.1.1.tgz#8e5a85c9b243e0bc776802c0de564561e57a5f78"
-  integrity sha512-ORNjq5z4EmQPriKbR0ER3k4Gh7YGNhWDL7JBW+8wXDrHLbWYKYSJaOJ9aN06npF5tbTxe2JBOsurpJDAvjiXKw==
+"@koa/router@9.0.1":
+  version "9.0.1"
+  resolved "https://registry.yarnpkg.com/@koa/router/-/router-9.0.1.tgz#4090a14223ea7e78aa13b632761209cba69acd95"
+  integrity sha512-OI+OU49CJV4px0WkIMmayBeqVXB/JS1ZMq7UoGlTZt6Y7ijK7kdeQ18+SEHHJPytmtI1y6Hf8XLrpxva3mhv5Q==
   dependencies:
     debug "^4.1.1"
     http-errors "^1.7.3"