diff --git a/lib/middleware/common.js b/lib/middleware/common.js
index eb1035a0c..3b27aede4 100644
--- a/lib/middleware/common.js
+++ b/lib/middleware/common.js
@@ -99,22 +99,7 @@ function setHeavyCacheHeaders (response) {
   response.setHeader('Cache-Control', 'public, max-age=31536000')
 }
 
-class PromiseContainer {
-  constructor () {
-    this.promise = null
-  }
-
-  then (success, error) {
-    return this.promise.then(success, error)
-  }
-
-  set (newPromise) {
-    this.promise = newPromise
-  }
-}
-
 // PUBLIC API
-exports.PromiseContainer = PromiseContainer
 exports.createServeFile = createServeFile
 exports.setNoCacheHeaders = setNoCacheHeaders
 exports.setHeavyCacheHeaders = setHeavyCacheHeaders