diff --git a/lib/middleware/karma.js b/lib/middleware/karma.js
index 3392096bd..f1bae3fc7 100644
--- a/lib/middleware/karma.js
+++ b/lib/middleware/karma.js
@@ -11,6 +11,8 @@
  * - setting propert caching headers
  */
 
+var _ = require('lodash')
+var from = require('core-js/library/fn/array/from')
 var path = require('path')
 var util = require('util')
 var url = require('url')
@@ -74,6 +76,12 @@ var isFirefox = function (req) {
   return firefox
 }
 
+var findByPath = function (files, path) {
+  return _.find(from(files), function (file) {
+    return file.path === path
+  })
+}
+
 var createKarmaMiddleware = function (
   filesPromise,
   serveStaticFile,
@@ -183,7 +191,12 @@ var createKarmaMiddleware = function (
               filePath = filePathToUrlPath(filePath, basePath, urlRoot, proxyPath)
 
               if (requestUrl === '/context.html') {
-                filePath += '?' + file.sha
+                var servedFile = findByPath(files.served, file.path)
+                if (servedFile) {
+                  filePath += '?' + servedFile.sha
+                } else {
+                  filePath += '?' + file.sha
+                }
               }
             }