diff --git a/tests/unit/position/position_core.js b/tests/unit/position/position_core.js
index f4075ccfe7c..b7d0894d386 100644
--- a/tests/unit/position/position_core.js
+++ b/tests/unit/position/position_core.js
@@ -406,22 +406,22 @@ test("collision: flip, with margin", function() {
 	}, { top: 0, left: 0 }, "right bottom");
 });
 
-//test('bug #5280: consistent results (avoid fractional values)', function() {
-//	var wrapper = $('#bug-5280'),
-//		elem = wrapper.children(),
-//		offset1 = elem.position({
-//			my: 'center',
-//			at: 'center',
-//			of: wrapper,
-//			collision: 'none'
-//		}).offset(),
-//		offset2 = elem.position({
-//			my: 'center',
-//			at: 'center',
-//			of: wrapper,
-//			collision: 'none'
-//		}).offset();
-//	same(offset1, offset2);
-//});
+test('bug #5280: consistent results (avoid fractional values)', function() {
+	var wrapper = $('#bug-5280'),
+		elem = wrapper.children(),
+		offset1 = elem.position({
+			my: 'center',
+			at: 'center',
+			of: wrapper,
+			collision: 'none'
+		}).offset(),
+		offset2 = elem.position({
+			my: 'center',
+			at: 'center',
+			of: wrapper,
+			collision: 'none'
+		}).offset();
+	same(offset1, offset2);
+});
 
 })(jQuery);
diff --git a/ui/jquery.ui.position.js b/ui/jquery.ui.position.js
index 837f23f40cd..5cb609471d1 100644
--- a/ui/jquery.ui.position.js
+++ b/ui/jquery.ui.position.js
@@ -14,6 +14,7 @@ $.ui = $.ui || {};
 var horizontalPositions = /left|center|right/,
 	verticalPositions = /top|center|bottom/,
 	center = "center",
+	support = {},
 	_position = $.fn.position,
 	_offset = $.fn.offset;
 
@@ -122,8 +123,10 @@ $.fn.position = function( options ) {
 		}
 
 		// prevent fractions (see #5280)
-		position.left = Math.round( position.left );
-		position.top = Math.round( position.top );
+		if (!support.fractions) {
+			position.left = Math.round( position.left );
+			position.top = Math.round( position.top );
+		}
 
 		collisionPosition = {
 			left: position.left - marginLeft,
@@ -249,4 +252,28 @@ if ( !$.offset.setOffset ) {
 	};
 }
 
+// support fractions (older versions of jquery don't support fractions)
+$(function () {
+	var body = document.body, offset,
+		div = $(body.appendChild( document.createElement( "div" ) ) );
+	
+	$.extend( div[0].style, {
+	  position: 'absolute',
+	  left: '10.2432222px',
+	  top: '10.432325px',
+	  height: '30px',
+	  width: '201px'
+	});
+	
+	offset = div.offset();
+	div.offset(offset);
+	offset = div.offset();
+	
+	// set display to none to avoid a layout bug in IE
+	// http://dev.jquery.com/ticket/4014
+	body.removeChild( div[0] ).style.display = "none";
+	
+	support.fractions = offset.top + offset.left > 20.0;
+});
+
 }( jQuery ));