diff --git a/lib/settings.js b/lib/settings.js
index f72051d..0bbc9b1 100644
--- a/lib/settings.js
+++ b/lib/settings.js
@@ -338,23 +338,25 @@
 	const resetSymbol = Symbol("reset");
 	function changeValue(name, newValue){
 		var settingDefinition = scope.getDefinition(name);
-		var oldValue = settings[name];
-		if (newValue === resetSymbol){
-			newValue = settingDefinition.defaultValue;
-		}
-		settings[name] = newValue;
-		((eventHandler[name] || {})[defaultSymbol] || []).forEach(function(callback){
-			callback({name, newValue, oldValue});
-		});
-
-		if (settingDefinition.urlSpecific){
-			urlContainer.get().forEach(function(entry){
-				if (!entry.hasOwnProperty(name)){
-					((eventHandler[name] || {})[entry.url] || []).forEach(function(callback){
-						callback({name, newValue, oldValue, url: entry.url});
-					});
-				}
+		if (settingDefinition){
+			var oldValue = settings[name];
+			if (newValue === resetSymbol){
+				newValue = settingDefinition.defaultValue;
+			}
+			settings[name] = newValue;
+			((eventHandler[name] || {})[defaultSymbol] || []).forEach(function(callback){
+				callback({name, newValue, oldValue});
 			});
+
+			if (settingDefinition.urlSpecific){
+				urlContainer.get().forEach(function(entry){
+					if (!entry.hasOwnProperty(name)){
+						((eventHandler[name] || {})[entry.url] || []).forEach(function(callback){
+							callback({name, newValue, oldValue, url: entry.url});
+						});
+					}
+				});
+			}
 		}
 	}