diff --git a/src/js/scriptlet-filtering.js b/src/js/scriptlet-filtering.js
index 2e24181b2..b12825dea 100644
--- a/src/js/scriptlet-filtering.js
+++ b/src/js/scriptlet-filtering.js
@@ -69,15 +69,16 @@
                     return;
                 }
                 let injectScriptlets = function(d) {
-                    let script = d.createElement('script');
+                    let script;
                     try {
+                        script = d.createElement('script');
                         script.appendChild(d.createTextNode(
                             decodeURIComponent(scriptlets))
                         );
                         (d.head || d.documentElement).appendChild(script);
                     } catch (ex) {
                     }
-                    if ( script.parentNode ) {
+                    if ( script && script.parentNode ) {
                         script.parentNode.removeChild(script);
                     }
                 };
diff --git a/src/js/tab.js b/src/js/tab.js
index 56b3ffcfc..177697c0e 100644
--- a/src/js/tab.js
+++ b/src/js/tab.js
@@ -494,7 +494,10 @@ vAPI.tabs.onNavigation = function(details) {
         }
     }
     if ( µb.canInjectScriptletsNow ) {
-        µb.scriptletFilteringEngine.injectNow(details);
+        let pageStore = µb.pageStoreFromTabId(details.tabId);
+        if ( pageStore !== null && pageStore.getNetFilteringSwitch() ) {
+            µb.scriptletFilteringEngine.injectNow(details);
+        }
     }
 };
 
@@ -505,12 +508,8 @@ vAPI.tabs.onNavigation = function(details) {
 // the extension icon won't be properly refreshed.
 
 vAPI.tabs.onUpdated = function(tabId, changeInfo, tab) {
-    if ( !tab.url || tab.url === '' ) {
-        return;
-    }
-    if ( !changeInfo.url ) {
-        return;
-    }
+    if ( !tab.url || tab.url === '' ) { return; }
+    if ( !changeInfo.url ) { return; }
     µb.tabContextManager.commit(tabId, changeInfo.url);
     µb.bindTabToPageStats(tabId, 'tabUpdated');
 };