diff --git a/lib/middleware/karma.js b/lib/middleware/karma.js
index a36a53617..2e603b382 100644
--- a/lib/middleware/karma.js
+++ b/lib/middleware/karma.js
@@ -151,6 +151,9 @@ var createKarmaMiddleware = function (filesPromise, serveStaticFile, serveFile,
           var mappings = files.served.map(function (file) {
             // Windows paths contain backslashes and generate bad IDs if not escaped
             var filePath = filePathToUrlPath(file.path, basePath, urlRoot).replace(/\\/g, '\\\\')
+            // Escape single quotes that might be in the filename -
+            // double quotes should not be allowed!
+            filePath = filePath.replace(/'/g, '\\\'')
 
             return util.format("  '%s': '%s'", filePath, file.sha)
           })
diff --git a/test/unit/middleware/karma.spec.js b/test/unit/middleware/karma.spec.js
index c7e905792..534a33453 100644
--- a/test/unit/middleware/karma.spec.js
+++ b/test/unit/middleware/karma.spec.js
@@ -282,6 +282,21 @@ describe('middleware.karma', () => {
     callHandlerWith('/__karma__/context.html')
   })
 
+  it('should escape quotes in mappings with all served files', (done) => {
+    fsMock._touchFile('/karma/static/context.html', 0, '%MAPPINGS%')
+    servedFiles([
+      new MockFile("/some/abc/a'b.js", 'sha_a'),
+      new MockFile('/base/path/ba.js', 'sha_b')
+    ])
+
+    response.once('end', () => {
+      expect(response).to.beServedAs(200, 'window.__karma__.files = {\n  \'/__karma__/absolute/some/abc/a\\\'b.js\': \'sha_a\',\n  \'/__karma__/base/ba.js\': \'sha_b\'\n};\n')
+      done()
+    })
+
+    callHandlerWith('/__karma__/context.html')
+  })
+
   it('should serve debug.html with replaced script tags without timestamps', (done) => {
     includedFiles([
       new MockFile('/first.js'),