diff --git a/server/src/storage/redis.ts b/server/src/storage/redis.ts
index ac20287..78ff76c 100644
--- a/server/src/storage/redis.ts
+++ b/server/src/storage/redis.ts
@@ -32,18 +32,23 @@ export default class RedisStorage implements StorageInterface {
     }
 
     async updateData<Type>(key: string, mutator: (current: Type | undefined) => Type): Promise<Type> {
-        return (client as any).executeIsolated(async (c: any) => {
+        // node-redis v5 nemá executeIsolated — pro WATCH/MULTI potřebujeme dedikované spojení
+        const c = client.duplicate();
+        await c.connect();
+        try {
             for (let attempt = 0; attempt < 10; attempt++) {
                 await c.watch(key);
                 const current = await c.json.get(key, { path: '.' }) as Type | undefined;
                 const next = mutator(current);
                 const multi = c.multi();
-                multi.json.set(key, '.', next);
+                multi.json.set(key, '.', next as any);
                 const result = await multi.exec();
                 if (result !== null) return next;
             }
             throw new Error(`updateData: optimistic lock failed after 10 retries for key: ${key}`);
-        });
+        } finally {
+            await c.disconnect();
+        }
     }
 
     async healthCheck(): Promise<boolean> {