diff --git a/src/cache/ttl.js b/src/cache/ttl.js
index 292c76fdc7..5e1bc2d5cd 100644
--- a/src/cache/ttl.js
+++ b/src/cache/ttl.js
@@ -30,7 +30,7 @@ module.exports = function (opts) {
 		});
 	});
 
-	cache.has = (key) => {
+	cache.has = function (key) {
 		if (!cache.enabled) {
 			return false;
 		}