diff --git a/qt/aqt/browser/previewer.py b/qt/aqt/browser/previewer.py
index 693cd2279..b18512267 100644
--- a/qt/aqt/browser/previewer.py
+++ b/qt/aqt/browser/previewer.py
@@ -129,6 +129,7 @@ class Previewer(QDialog):
             "js/vendor/css_browser_selector.min.js",
             "js/mathjax.js",
             "js/vendor/mathjax/tex-chtml.js",
+            "js/vendor/protobuf.min.js",
             "js/reviewer.js",
         ]
         self._web.stdHtml(
diff --git a/qt/aqt/clayout.py b/qt/aqt/clayout.py
index 4c69299e1..0f2077bc2 100644
--- a/qt/aqt/clayout.py
+++ b/qt/aqt/clayout.py
@@ -335,6 +335,7 @@ class CardLayout(QDialog):
             "js/vendor/css_browser_selector.min.js",
             "js/mathjax.js",
             "js/vendor/mathjax/tex-chtml.js",
+            "js/vendor/protobuf.min.js",
             "js/reviewer.js",
         ]
         self.preview_web.stdHtml(