diff --git a/src/css.js b/src/css.js
index 84b6e602..69c4452b 100644
--- a/src/css.js
+++ b/src/css.js
@@ -155,7 +155,7 @@ jQuery.each(["height", "width"], function( i, name ) {
 		},
 
 		set: function( elem, value ) {
-			if ( value !== "" ) {
+			if ( rnumpx.test( value ) ) {
 				// ignore negative width and height values #1599
 				value = parseFloat(value);
 
diff --git a/test/unit/css.js b/test/unit/css.js
index 99bab1fe..0e91ae15 100644
--- a/test/unit/css.js
+++ b/test/unit/css.js
@@ -1,7 +1,7 @@
 module("css");
 
 test("css(String|Hash)", function() {
-	expect(28);
+	expect(29);
 
 	equals( jQuery('#main').css("display"), 'none', 'Check for css property "display"');
 
@@ -44,6 +44,9 @@ test("css(String|Hash)", function() {
 	equals( parseInt(child.css("fontSize")), 16, "Verify fontSize px set." );
 	equals( parseInt(child.css("font-size")), 16, "Verify fontSize px set." );
 
+	child.css("height", "100%");
+	equals( child[0].style.height, "100%", "Make sure the height is being set correctly." );
+
 	child.attr("class", "em");
 	equals( parseInt(child.css("fontSize")), 32, "Verify fontSize em set." );