diff --git a/data/frame.js b/data/frame.js
index e3dea49..64c2c9a 100644
--- a/data/frame.js
+++ b/data/frame.js
@@ -26,6 +26,18 @@
 			return {type: [], mode: "allow"};
 		}
 	}
+	function checkStack(stack){
+		if (enabled){
+			var status = sendSyncMessage(
+				"canvasBlocker-checkStack",
+				stack
+			);
+			return status[0];
+		}
+		else {
+			return true;
+		}
+	}
 	function askWrapper(data){
 		return ask(data, {
 			_: function(token){
@@ -56,7 +68,7 @@
 			var window = ev.target.defaultView;
 			intercept(
 				{subject: window},
-				{check, ask: askWrapper, notify, prefs}
+				{check, checkStack, ask: askWrapper, notify, prefs}
 			);
 		}
 	}
diff --git a/lib/check.js b/lib/check.js
index e63ce1d..3f9157f 100644
--- a/lib/check.js
+++ b/lib/check.js
@@ -13,8 +13,7 @@
 	const {URL} = require("sdk/url");
 
 	exports.check = function check({url, errorStack}){
-		var callingStack = parseErrorStack(errorStack);
-		var match = checkBoth(callingStack, url, prefs.blockMode).match(/^(block|allow|fake|ask)(|Readout|Everything|Context|Input)$/);
+		var match = checkBoth(errorStack, url, prefs.blockMode).match(/^(block|allow|fake|ask)(|Readout|Everything|Context|Input|Internal)$/);
 		if (match){
 			return {
 				type: (match[2] === "Everything" || match[2] === "")?
@@ -32,8 +31,8 @@
 		
 	};
 
-	function checkBoth(stack, url, blockMode){
-		if (prefs.enableStackList && checkStack(stack)){
+	function checkBoth(errorStack, url, blockMode){
+		if (prefs.enableStackList && errorStack && checkStack(errorStack)){
 			return "allow";
 		}
 		else {
@@ -42,15 +41,15 @@
 	}
 
 	function checkURL(url, blockMode){
-		url = new URL(url);
+		url = new URL(url || "about:blank");
 		switch (url.protocol){
 			case "about:":
 				if (url.href === "about:blank"){
 					break;
 				}
-				return "allow";
+				return "allowInternal";
 			case "chrome:":
-				return "allow";
+				return "allowInternal";
 		}
 		
 		var mode = "block";
@@ -93,7 +92,9 @@
 		return mode;
 	}
 
-	function checkStack(stack){
-		return lists.get("stack").match(stack);
+	function checkStack(errorStack){
+		var callingStack = parseErrorStack(errorStack);
+		return lists.get("stack").match(callingStack);
 	}
+	exports.checkStack = checkStack;
 }());
\ No newline at end of file
diff --git a/lib/main.js b/lib/main.js
index 0380951..af46504 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -8,7 +8,7 @@
 	
 	
 	const {when: unload} = require("sdk/system/unload");
-	const {check} = require("./check.js");
+	const {check, checkStack} = require("./check.js");
 	const {notify} = require("./notifications");
 	
 	const _ = require("sdk/l10n").get;
@@ -53,6 +53,9 @@
 		var status = check(ev.data);
 		return status;
 	});
+	addMessageListener("canvasBlocker-checkStack", function(ev){
+		return checkStack(ev.data);
+	});
 	
 	addMessageListener("canvasBlocker-notify", function(ev){
 		var browser = ev.target;