diff --git a/lib/helper.js b/lib/helper.js
index 34b349efd..b1313d5a3 100644
--- a/lib/helper.js
+++ b/lib/helper.js
@@ -141,6 +141,10 @@ const replaceWinPath = (path) => {
 
 exports.normalizeWinPath = process.platform === 'win32' ? replaceWinPath : _.identity
 
+exports.getFileType = (file) => {
+  return file.type || path.extname(file.path.split(/[?#]/, 1)[0] || '').substring(1)
+}
+
 exports.mkdirIfNotExists = (directory, done) => {
   // TODO(vojta): handle if it's a file
   /* eslint-disable handle-callback-err */
diff --git a/lib/middleware/karma.js b/lib/middleware/karma.js
index dd1ee1d00..588fa609e 100644
--- a/lib/middleware/karma.js
+++ b/lib/middleware/karma.js
@@ -11,7 +11,6 @@
  * - setting propert caching headers
  */
 
-const path = require('path')
 const url = require('url')
 const helper = require('../helper')
 
@@ -164,7 +163,7 @@ function createKarmaMiddleware (
           const scriptTags = []
           for (const file of files.included) {
             let filePath = file.path
-            const fileType = file.type || path.extname(filePath).substring(1)
+            const fileType = helper.getFileType(file)
 
             if (helper.isDefined(fileType) && !FILE_TYPES.includes(fileType)) {
               log.warn(`Invalid file type (${fileType}), defaulting to js.`)
diff --git a/test/unit/helper.spec.js b/test/unit/helper.spec.js
index 8c5808c50..50318d150 100644
--- a/test/unit/helper.spec.js
+++ b/test/unit/helper.spec.js
@@ -228,6 +228,15 @@ describe('helper', () => {
     })
   })
 
+  describe('getFileType', () => {
+    it('should extract file type', () => {
+      expect(helper.getFileType({ path: 'a.js' })).to.equal('js')
+      expect(helper.getFileType({ path: 'a.js#' })).to.equal('js')
+      expect(helper.getFileType({ path: 'a.js?#' })).to.equal('js')
+      expect(helper.getFileType({ type: 'js', path: 'a' })).to.equal('js')
+    })
+  })
+
   describe('mkdirIfNotExists', () => {
     const fsMock = require('mocks').fs
     const loadFile = require('mocks').loadFile