diff --git a/mithril.js b/mithril.js
index ddd94405..961b6746 100644
--- a/mithril.js
+++ b/mithril.js
@@ -60,7 +60,9 @@ var m = (function app(window, undefined) {
 		}
 
 		for (var attrName in attrs) {
-			if (attrName === classAttrName) cell.attrs[attrName] = (cell.attrs[attrName] || "") + " " + attrs[attrName];
+			if (attrName === classAttrName) {
+				if (attrs[attrName] !== "") cell.attrs[attrName] = (cell.attrs[attrName] || "") + " " + attrs[attrName];
+			}
 			else cell.attrs[attrName] = attrs[attrName]
 		}
 		return cell
diff --git a/tests/mithril-tests.js b/tests/mithril-tests.js
index e926fb03..345670aa 100644
--- a/tests/mithril-tests.js
+++ b/tests/mithril-tests.js
@@ -28,6 +28,11 @@ function testMithril(mock) {
 	test(function() {return m("svg", [m("a[href='http://google.com']")])})
 	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", {class: ""}).attrs.className === undefined})
+	test(function() {return m("div", {className: ""}).attrs.class === undefined})
+	test(function() {return m("div", {class: ""}).attrs.class === undefined})
 
 	//m.module
 	test(function() {