diff --git a/demo/merge.html b/demo/merge.html
index c60e653297fa391164f7eea7dbd4bf17aac202e4..20783b866cdfc60bf35acc16ca723c9d19407f62 100644
--- a/demo/merge.html
+++ b/demo/merge.html
@@ -11,7 +11,7 @@
 <script src="../mode/css/css.js"></script>
 <script src="../mode/javascript/javascript.js"></script>
 <script src="../mode/htmlmixed/htmlmixed.js"></script>
-<script src="//cdnjs.cloudflare.com/ajax/libs/diff_match_patch/20121119/diff_match_patch.js"></script>
+<script src="https://cdnjs.cloudflare.com/ajax/libs/diff_match_patch/20121119/diff_match_patch.js"></script>
 <script src="../addon/merge/merge.js"></script>
 <style>
     .CodeMirror { line-height: 1.2; }