diff --git a/src/offset.js b/src/offset.js
index 59591caea6..0ce4c1979c 100644
--- a/src/offset.js
+++ b/src/offset.js
@@ -150,15 +150,27 @@ jQuery.offset = {
 	},
 	
 	setOffset: function( elem, options, i ) {
+		var position = jQuery.curCSS( elem, "position" );
+
 		// set position first, in-case top/left are set even on static elem
-		if ( /static/.test( jQuery.curCSS( elem, "position" ) ) ) {
+		if ( position === "static" ) {
 			elem.style.position = "relative";
 		}
-		var curElem   = jQuery( elem ),
-			curOffset = curElem.offset(),
-			curTop    = parseInt( jQuery.curCSS( elem, "top",  true ), 10 ) || 0,
-			curLeft   = parseInt( jQuery.curCSS( elem, "left", true ), 10 ) || 0,
-			props     = {};
+
+		var curElem    = jQuery( elem ),
+			curOffset  = curElem.offset(),
+			curCSSTop  = jQuery.curCSS( elem, "top", true ),
+			curCSSLeft = jQuery.curCSS( elem, "left", true ),
+			calculatePosition = (position === "absolute" && jQuery.inArray('auto', [curCSSTop, curCSSLeft]) > -1),
+			props = {}, curPosition = {}, curTop, curLeft;
+
+		// need to be able to calculate position if either top or left is auto and position is absolute
+		if ( calculatePosition ) {
+			curPosition = curElem.position();
+		}
+
+		curTop  = calculatePosition ? curPosition.top  : parseInt( curCSSTop,  10 ) || 0;
+		curLeft = calculatePosition ? curPosition.left : parseInt( curCSSLeft, 10 ) || 0;
 
 		if ( jQuery.isFunction( options ) ) {
 			options = options.call( elem, i, curOffset );
diff --git a/test/data/offset/absolute.html b/test/data/offset/absolute.html
index 3bbc8417dc..2a7eb73e56 100644
--- a/test/data/offset/absolute.html
+++ b/test/data/offset/absolute.html
@@ -13,6 +13,7 @@
 			#absolute-2 { top: 19px; left: 19px; }
 			#marker { position: absolute; border: 2px solid #000; width: 50px; height: 50px; background: #ccc; }
 			p.instructions { position: absolute; bottom: 0; }
+			#positionTest { position: absolute; }
 		</style>
 		<script type="text/javascript" src="../../../dist/jquery.js"></script>
 		<script type="text/javascript" charset="utf-8">
@@ -33,6 +34,7 @@
 			</div>
 		</div>
 		<div id="absolute-2" class="absolute">absolute-2</div>
+		<div id="positionTest">Has absolute position but no values set for the location ('auto').</div>
 		<div id="marker"></div>
 		<p class="instructions">Click the white box to move the marker to it. Clicking the box also changes the position to absolute (if not already) and sets the position according to the position method.</p>
 	</body>
diff --git a/test/unit/offset.js b/test/unit/offset.js
index ef84e5cd0f..3b6af50e1d 100644
--- a/test/unit/offset.js
+++ b/test/unit/offset.js
@@ -35,7 +35,7 @@ testoffset("absolute"/* in iframe */, function($, iframe) {
 });
 
 testoffset("absolute", function( jQuery ) {
-	expect(176);
+	expect(178);
 	
 	// get offset tests
 	var tests = [
@@ -62,6 +62,11 @@ testoffset("absolute", function( jQuery ) {
 		equals( jQuery( this.id ).position().left, this.left, "jQuery('" + this.id + "').position().left" );
 	});
 	
+	// test #5781
+	var offset = jQuery( '#positionTest' ).offset({ top: 10, left: 10 }).offset();
+	equals( offset.top,  10, "Setting offset on element with position absolute but 'auto' values." )
+	equals( offset.left, 10, "Setting offset on element with position absolute but 'auto' values." )
+	
 	
 	// set offset
 	tests = [
@@ -97,8 +102,9 @@ testoffset("absolute", function( jQuery ) {
 		equals( jQuery( this.id ).offset().top,  this.top  + 1, "jQuery('" + this.id + "').offset({ top: "  + (this.top  + 1) + " })" );
 		equals( jQuery( this.id ).offset().left, this.left + 1, "jQuery('" + this.id + "').offset({ left: " + (this.left + 1) + " })" );
 		
-		jQuery( this.id ).offset({ top: this.top + 2 });
-		jQuery( this.id ).offset({ left: this.left + 2 });
+		jQuery( this.id )
+			.offset({ left: this.left + 2 })
+			.offset({ top:  this.top  + 2 });
 		equals( jQuery( this.id ).offset().top,  this.top  + 2, "Setting one property at a time." );
 		equals( jQuery( this.id ).offset().left, this.left + 2, "Setting one property at a time." );