diff --git a/packages/backend/src/server/api/service/github.ts b/packages/backend/src/server/api/service/github.ts
index da9d0931a..fd015fb8a 100644
--- a/packages/backend/src/server/api/service/github.ts
+++ b/packages/backend/src/server/api/service/github.ts
@@ -18,7 +18,7 @@ function getUserToken(ctx: Koa.BaseContext): string | null {
 
 function compareOrigin(ctx: Koa.BaseContext): boolean {
 	function normalizeUrl(url?: string): string {
-		return slice( url.length - 1) : url) : "";
+		return url ? (url.endsWith("/") ? url.slice(0, url.length - 1) : url) : "";
 	}
 
 	const referer = ctx.headers["referer"];