diff --git a/docs/change-log.md b/docs/change-log.md
index 1627c459..d889581a 100644
--- a/docs/change-log.md
+++ b/docs/change-log.md
@@ -18,6 +18,7 @@
 -	fix dom element ownership bug when mixing keyed elements and third party plugin elements [#463](https://github.com/lhorie/mithril.js/issues/463)
 -	fix edge case in flatten algorithm [#448](https://github.com/lhorie/mithril.js/issues/448)
 -	prevent unnecessary DOM move operation when mixing keyed and unkeyed elements [#398](https://github.com/lhorie/mithril.js/issues/398)
+-	revert [#382](https://github.com/lhorie/mithril.js/issues/382) due to diff regression [#512](https://github.com/lhorie/mithril.js/issues/512)
 
 ---
 
diff --git a/docs/getting-started.md b/docs/getting-started.md
index 796312aa..6eef1858 100644
--- a/docs/getting-started.md
+++ b/docs/getting-started.md
@@ -130,25 +130,23 @@ In the case of our todo application, the view-model needs a few things: it needs
 
 ```javascript
 //define the view-model
-todo.vm = (function() {
-	var vm = {}
-	vm.init = function() {
+todo.vm = {
+	init: function() {
 		//a running list of todos
-		vm.list = new todo.TodoList();
+		todo.vm.list = new todo.TodoList();
 		
 		//a slot to store the name of a new todo before it is created
-		vm.description = m.prop("");
+		todo.vm.description = m.prop('');
 		
 		//adds a todo to the list, and clears the description field for user convenience
-		vm.add = function(description) {
+		todo.vm.add = function(description) {
 			if (description()) {
-				vm.list.push(new todo.Todo({description: description()}));
-				vm.description("");
+				todo.vm.list.push(new todo.Todo({description: description()}));
+				todo.vm.description("");
 			}
 		};
 	}
-	return vm
-}())
+};
 ```
 
 The code above defines a view-model object called `vm`. It is simply a javascript object that has a `init` function. This function initializes the `vm` object with three members: `list`, which is simply an array, `description`, which is an `m.prop` getter-setter function with an empty string as the initial value, and `add`, which is a method that adds a new Todo instance to `list` if an input description getter-setter is not an empty string.
diff --git a/mithril.js b/mithril.js
index 1a2742df..8d93e603 100644
--- a/mithril.js
+++ b/mithril.js
@@ -61,7 +61,8 @@ var m = (function app(window, undefined) {
 		
 		for (var attrName in attrs) {
 			if (attrName === classAttrName) {
-				if (attrs[attrName] !== "") cell.attrs[attrName] = (cell.attrs[attrName] || "") + " " + attrs[attrName];
+				var className = cell.attrs[attrName]
+				cell.attrs[attrName] = (className && attrs[attrName] ? className + " " : className || "") + attrs[attrName];
 			}
 			else cell.attrs[attrName] = attrs[attrName]
 		}
diff --git a/tests/mithril-tests.js b/tests/mithril-tests.js
index 703a3605..3c24e130 100644
--- a/tests/mithril-tests.js
+++ b/tests/mithril-tests.js
@@ -29,10 +29,10 @@ function testMithril(mock) {
 	test(function() {return m(".foo", {"class": "bar"}).attrs["class"] == "foo bar"})
 	test(function() {return m(".foo", {className: "bar"}).attrs.className == "foo bar"})
 	test(function() {return m(".foo", {className: ""}).attrs.className == "foo"})
-	test(function() {return m("div", {className: ""}).attrs.className === undefined}) //https://github.com/lhorie/mithril.js/issues/382
+	test(function() {return m("div", {className: ""}).attrs.className === ""}) //https://github.com/lhorie/mithril.js/issues/382 and 512
 	test(function() {return m("div", {class: ""}).attrs.className === undefined})
 	test(function() {return m("div", {className: ""}).attrs.class === undefined})
-	test(function() {return m("div", {class: ""}).attrs.class === undefined})
+	test(function() {return m("div", {class: ""}).attrs.class === ""})
 	test(function() {return m("div", [1, 2, 3], 4).children.length === 2})
 	test(function() {return m("div", [1, 2, 3], 4).children[0].length === 3})
 	test(function() {return m("div", [1, 2, 3], 4).children[1] === 4})