diff --git a/browser/base/content/test/static/browser_all_files_referenced.js b/browser/base/content/test/static/browser_all_files_referenced.js
index ff015f28492f9..5fe07ee173cb3 100644
--- a/browser/base/content/test/static/browser_all_files_referenced.js
+++ b/browser/base/content/test/static/browser_all_files_referenced.js
@@ -128,6 +128,9 @@ var allowlist = [
   // security/manager/pki/resources/content/device_manager.js
   { file: "chrome://pippki/content/load_device.xhtml" },
 
+  // Intentionally unreferenced, see bug 1941134
+  { file: "resource://gre/res/designmode.css" },
+
   // The l10n build system can't package string files only for some platforms.
   // See bug 1339424 for why this is hard to fix.
   {
diff --git a/browser/installer/package-manifest.in b/browser/installer/package-manifest.in
index 90c2e7a69076d..861ba1c484a46 100644
--- a/browser/installer/package-manifest.in
+++ b/browser/installer/package-manifest.in
@@ -282,6 +282,7 @@
 ; Style Sheets, Graphics and other Resources used by the layout engine.
 @RESPATH@/res/EditorOverride.css
 @RESPATH@/res/contenteditable.css
+@RESPATH@/res/designmode.css
 @RESPATH@/res/table-add-column-after-active.gif
 @RESPATH@/res/table-add-column-after-hover.gif
 @RESPATH@/res/table-add-column-after.gif
diff --git a/layout/style/designmode.css b/layout/style/designmode.css
new file mode 100644
index 0000000000000..91108de3e61db
--- /dev/null
+++ b/layout/style/designmode.css
@@ -0,0 +1,5 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Empty, see bug 1941134 */
diff --git a/layout/style/moz.build b/layout/style/moz.build
index 783dc874591cd..4043ddd1ec7a8 100644
--- a/layout/style/moz.build
+++ b/layout/style/moz.build
@@ -291,6 +291,7 @@ JAR_MANIFESTS += ["jar.mn"]
 
 RESOURCE_FILES += [
     "contenteditable.css",
+    "designmode.css",
 ]
 
 CONTENT_ACCESSIBLE_FILES += [