diff --git a/src/js/tab.js b/src/js/tab.js
index 48dd9e32b..c6da477f8 100644
--- a/src/js/tab.js
+++ b/src/js/tab.js
@@ -916,6 +916,10 @@ vAPI.Tabs = class extends vAPI.Tabs {
     //   For non-network URIs, defer scriptlet injection to content script. The
     //   reason for this is that we need the effective URL and this information
     //   is not available at this point.
+    //
+    // https://github.com/uBlockOrigin/uBlock-issues/issues/2343
+    //   uBO's isolated world in Firefox just does not work as expected at
+    //   point, so we have to wait before injecting scriptlets.
     onNavigation(details) {
         super.onNavigation(details);
         const { frameId, tabId, url } = details;
@@ -929,7 +933,10 @@ vAPI.Tabs = class extends vAPI.Tabs {
         const pageStore = µb.pageStoreFromTabId(tabId);
         if ( pageStore === null ) { return; }
         pageStore.setFrameURL(details);
-        if ( pageStore.getNetFilteringSwitch() ) {
+        if (
+            vAPI.webextFlavor.soup.has('firefox') === false &&
+            pageStore.getNetFilteringSwitch()
+        ) {
             scriptletFilteringEngine.injectNow(details);
         }
     }