diff --git a/lib/iframeProtection.js b/lib/iframeProtection.js
index 56da871..9064386 100644
--- a/lib/iframeProtection.js
+++ b/lib/iframeProtection.js
@@ -21,6 +21,13 @@
 	
 	scope.protect = function protect(window, wrappedWindow, singleCallback, allCallback){
 		
+		function changeProperty(object, name, type, changed){
+			const descriptor = Object.getOwnPropertyDescriptor(object, name);
+			const original = descriptor[type];
+			descriptor[type] = changed;
+			Object.defineProperty(object, name, descriptor);
+			registerChangedProperty(object, name, descriptor, type, original);
+		}
 		const changedProperties = [];
 		// eslint-disable-next-line max-params
 		function registerChangedProperty(object, name, descriptor, type, original){
@@ -61,13 +68,10 @@
 					return window;
 				}
 			};
-			contentWindowDescriptor.get = exportFunction(
+			changeProperty(wrappedConstructor.prototype, "contentWindow", "get", exportFunction(
 				Object.getOwnPropertyDescriptor(contentWindowTemp, "contentWindow").get,
 				window
-			);
-			Object.defineProperty(wrappedConstructor.prototype, "contentWindow", contentWindowDescriptor);
-			registerChangedProperty(wrappedConstructor.prototype, "contentWindow", contentWindowDescriptor,
-				"get", originalContentWindowGetter);
+			));
 			
 			const contentDocumentDescriptor = Object.getOwnPropertyDescriptor(
 				constructor.prototype,
@@ -83,13 +87,10 @@
 					return document;
 				}
 			};
-			contentDocumentDescriptor.get = exportFunction(
+			changeProperty(wrappedConstructor.prototype, "contentDocument", "get", exportFunction(
 				Object.getOwnPropertyDescriptor(contentDocumentTemp, "contentDocument").get,
 				window
-			);
-			Object.defineProperty(wrappedConstructor.prototype, "contentDocument", contentDocumentDescriptor);
-			registerChangedProperty(wrappedConstructor.prototype, "contentDocument", contentDocumentDescriptor,
-				"get", originalContentDocumentGetter);
+			));
 		});
 		[
 			// useless as length could be obtained before the iframe is created and window.frames === window
@@ -123,19 +124,15 @@
 			protectionDefinition.methods.forEach(function(method){
 				const descriptor = Object.getOwnPropertyDescriptor(object, method);
 				const original = descriptor.value;
-				descriptor.value = exportFunction(eval(`(function ${method}(){
+				changeProperty(object, method, "value", exportFunction(eval(`(function ${method}(){
 					const value = arguments.length?
 						original.apply(this, window.Array.from(arguments)):
 						original.call(this);
 					allCallback();
 					return value;
-				})`), window);
-				Object.defineProperty(object, method, descriptor);
-				registerChangedProperty(object, method, descriptor, "value", original);
+				})`), window));
 			});
 			protectionDefinition.getters.forEach(function(property){
-				const descriptor = Object.getOwnPropertyDescriptor(object, property);
-				const getter = descriptor.get;
 				const temp = eval(`({
 					get ${property}(){
 						const ret = this.${property};
@@ -143,9 +140,10 @@
 						return ret;
 					}
 				})`);
-				descriptor.get = exportFunction(Object.getOwnPropertyDescriptor(temp, property).get, window);
-				Object.defineProperty(object, property, descriptor);
-				registerChangedProperty(object, property, descriptor, "get", getter);
+				changeProperty(object, property, "get", exportFunction(
+					Object.getOwnPropertyDescriptor(temp, property).get,
+					window
+				));
 			});
 			protectionDefinition.setters.forEach(function(property){
 				const descriptor = Object.getOwnPropertyDescriptor(object, property);
@@ -158,9 +156,9 @@
 						return ret;
 					}
 				})`);
-				descriptor.set = exportFunction(Object.getOwnPropertyDescriptor(temp, property).set, window);
-				Object.defineProperty(object, property, descriptor);
-				registerChangedProperty(object, property, descriptor, "set", setter);
+				changeProperty(object, property, "set", exportFunction(
+					Object.getOwnPropertyDescriptor(temp, property).set, window
+				));
 			});
 		});
 		
@@ -188,63 +186,72 @@
 		}();
 		
 		// MutationObserver does not trigger fast enough when document.write is used
-		const documentWriteDescriptor = Object.getOwnPropertyDescriptor(
+		const documentWriteDescriptorOnHTMLDocument = Object.getOwnPropertyDescriptor(
 			wrappedWindow.HTMLDocument.prototype,
 			"write"
-		) || Object.getOwnPropertyDescriptor(
+		);
+		const documentWriteDescriptor = documentWriteDescriptorOnHTMLDocument || Object.getOwnPropertyDescriptor(
 			wrappedWindow.Document.prototype,
 			"write"
 		);
 		const documentWrite = documentWriteDescriptor.value;
-		documentWriteDescriptor.value = exportFunction(function write(markup){
-			for (let i = 0, l = arguments.length; i < l; i += 1){
-				const str = "" + arguments[i];
-				// weird problem with waterfox and google docs
-				const parts = (
-					str.match(/^\s*<!doctype/i) &&
-					!str.match(/frame/i)
-				)? [str]: str.split(/(?=<)/);
-				const length = parts.length;
-				const scripts = window.document.getElementsByTagName("script");
-				for (let i = 0; i < length; i += 1){
-					documentWrite.call(this, parts[i]);
-					allCallback();
-					if (scripts.length && scripts[scripts.length - 1].src){
-						observe();
+		changeProperty(
+			documentWriteDescriptorOnHTMLDocument?
+				wrappedWindow.HTMLDocument.prototype:
+				wrappedWindow.Document.prototype,
+			"write", "value", exportFunction(function write(markup){
+				for (let i = 0, l = arguments.length; i < l; i += 1){
+					const str = "" + arguments[i];
+					// weird problem with waterfox and google docs
+					const parts = (
+						str.match(/^\s*<!doctype/i) &&
+						!str.match(/frame/i)
+					)? [str]: str.split(/(?=<)/);
+					const length = parts.length;
+					const scripts = window.document.getElementsByTagName("script");
+					for (let i = 0; i < length; i += 1){
+						documentWrite.call(this, parts[i]);
+						allCallback();
+						if (scripts.length && scripts[scripts.length - 1].src){
+							observe();
+						}
 					}
 				}
-			}
-		}, window);
-		Object.defineProperty(wrappedWindow.HTMLDocument.prototype, "write", documentWriteDescriptor);
-		registerChangedProperty(wrappedWindow.HTMLDocument.prototype, "write", documentWriteDescriptor,
-			"value", documentWrite);
+			}, window)
+		);
 		
-		const documentWritelnDescriptor = Object.getOwnPropertyDescriptor(
+		const documentWritelnDescriptorOnHTMLDocument = Object.getOwnPropertyDescriptor(
 			wrappedWindow.HTMLDocument.prototype,
 			"writeln"
-		) || Object.getOwnPropertyDescriptor(
+		);
+		const documentWritelnDescriptor = documentWritelnDescriptorOnHTMLDocument || Object.getOwnPropertyDescriptor(
 			wrappedWindow.Document.prototype,
 			"writeln"
 		);
 		const documentWriteln = documentWritelnDescriptor.value;
-		documentWritelnDescriptor.value = exportFunction(function writeln(markup){
-			for (let i = 0, l = arguments.length; i < l; i += 1){
-				const str = "" + arguments[i];
-				const parts = str.split(/(?=<)/);
-				const length = parts.length;
-				const scripts = window.document.getElementsByTagName("script");
-				for (let i = 0; i < length; i += 1){
-					documentWrite.call(this, parts[i]);
-					allCallback();
-					if (scripts.length && scripts[scripts.length - 1].src){
-						observe();
+		changeProperty(
+			documentWritelnDescriptorOnHTMLDocument?
+				wrappedWindow.HTMLDocument.prototype:
+				wrappedWindow.Document.prototype,
+			"writeln", "value", exportFunction(
+				function writeln(markup){
+					for (let i = 0, l = arguments.length; i < l; i += 1){
+						const str = "" + arguments[i];
+						const parts = str.split(/(?=<)/);
+						const length = parts.length;
+						const scripts = window.document.getElementsByTagName("script");
+						for (let i = 0; i < length; i += 1){
+							documentWrite.call(this, parts[i]);
+							allCallback();
+							if (scripts.length && scripts[scripts.length - 1].src){
+								observe();
+							}
+						}
 					}
-				}
-			}
-			documentWriteln.call(this, "");
-		}, window);
-		Object.defineProperty(wrappedWindow.HTMLDocument.prototype, "writeln", documentWritelnDescriptor);
-		registerChangedProperty(wrappedWindow.HTMLDocument.prototype, "writeln", documentWritelnDescriptor,
-			"value", documentWriteln);
+					documentWriteln.call(this, "");
+				},
+				window
+			)
+		);
 	};
 }());
\ No newline at end of file
diff --git a/versions/updates.json b/versions/updates.json
index df01667..6f7408a 100644
--- a/versions/updates.json
+++ b/versions/updates.json
@@ -61,6 +61,14 @@
 				{
 					"version": "0.5.14Alpha20190821",
 					"update_link": "https://canvasblocker.kkapsner.de/versions/canvasblocker_beta-0.5.14Alpha20190821-an+fx.xpi"
+				},
+				{
+					"version": "0.5.14Alpha20190911",
+					"update_link": "https://canvasblocker.kkapsner.de/versions/canvasblocker_beta-0.5.14Alpha20190911-an+fx.xpi"
+				},
+				{
+					"version": "0.5.14Alpha20190912",
+					"update_link": "https://canvasblocker.kkapsner.de/versions/canvasblocker_beta-0.5.14Alpha20190912-an+fx.xpi"
 				}
 			]
 		}