diff --git a/devtools/image_viewer/index.html b/devtools/image_viewer/index.html
index a908e6ce599..45d624b6eff 100644
--- a/devtools/image_viewer/index.html
+++ b/devtools/image_viewer/index.html
@@ -7,6 +7,6 @@
     <div id="plot-images"></div>
     <pre id="plot-mock"></pre>
 
-    <script src="../../build/image_viewer-bundle.js"></script>
+    <script src="../../build/image_viewer-bundle.js" charset="utf-8"></script>
 </body>
 </html>