diff --git a/lib/middleware/redis-cache.js b/lib/middleware/redis-cache.js
index 764a82fdc..6ecbeaca4 100644
--- a/lib/middleware/redis-cache.js
+++ b/lib/middleware/redis-cache.js
@@ -46,7 +46,7 @@ module.exports = function(options = {}) {
             if (key) {
                 const value = await redisClient.get(key);
                 if (value) {
-                    let ttl = redisClient.ttl(key);
+                    let ttl = await redisClient.ttl(key);
                     ttl = ttl > expire ? ttl : expire * 2;
                     await redisClient.setex(key, ttl, value);
                 }