diff --git a/backend/src/routes/banking.ts b/backend/src/routes/banking.ts
index ce25ef0..95a3d32 100644
--- a/backend/src/routes/banking.ts
+++ b/backend/src/routes/banking.ts
@@ -997,7 +997,10 @@ export default async function bankingRoutes(server: FastifyInstance) {
 
             if (!tenantId) return reply.code(401).send({ error: "Unauthorized" })
 
-            const redirect = new URL("/settings/banking", secrets.API_BASE_URL).toString()
+            // API_BASE_URL kann einen Reverse-Proxy-Pfad wie `/backend` enthalten.
+            // Der OAuth-Rücksprung muss aber auf die Frontend-Route zeigen und darf
+            // diesen Backend-Pfad nicht erneut enthalten.
+            const redirect = new URL("/settings/banking", new URL(secrets.API_BASE_URL).origin).toString()
             let data: any
             if (useCentralBanking) {
                 data = await centralServicesClient.createBankingRequisition({ institutionId: institutionid, redirect, userLanguage: "de" })