diff --git a/toolkit/mozapps/extensions/content/extensions.xml b/toolkit/mozapps/extensions/content/extensions.xml
index b0b2c399b61a..b8d3e5fe69ef 100644
--- a/toolkit/mozapps/extensions/content/extensions.xml
+++ b/toolkit/mozapps/extensions/content/extensions.xml
@@ -903,7 +903,7 @@
           this.setAttribute("legacy", legacyWarning);
           document.getAnonymousElementByAttribute(this, "anonid", "legacy").href = SUPPORT_URL + "webextensions";
 
-          if (!allowPrivateBrowsingByDefault) {
+          if (!allowPrivateBrowsingByDefault && this.mAddon.type === "extension") {
             ExtensionPermissions.get(this.mAddon.id).then((perms) => {
               let allowed = perms.permissions.includes("internal:privateBrowsingAllowed");
               this.setAttribute("privateBrowsing", allowed);
diff --git a/toolkit/mozapps/extensions/test/browser/browser_theme_previews.js b/toolkit/mozapps/extensions/test/browser/browser_theme_previews.js
index 96c6c9952613..a5dd2bfddd75 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_theme_previews.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_theme_previews.js
@@ -135,6 +135,12 @@ add_task(async function testThemeOrdering() {
     ],
     "Themes are ordered by enabled, previews, then name");
 
+  // Ensure allow in private mode badge is hidden for themes.
+  for (let item of list.itemChildren) {
+    let badge = gManagerWindow.document.getAnonymousElementByAttribute(item, "anonid", "privateBrowsing");
+    is_element_hidden(badge, `private browsing badge is hidden`);
+  }
+
   await close_manager(gManagerWindow);
   for (let addon of await promiseAddonsByIDs(themeIds)) {
     await addon.uninstall();