diff --git a/wp-content/themes/twentyfifteen/js/functions.js b/wp-content/themes/twentyfifteen/js/functions.js
index b9dddc85be..f26293edab 100644
--- a/wp-content/themes/twentyfifteen/js/functions.js
+++ b/wp-content/themes/twentyfifteen/js/functions.js
@@ -6,10 +6,8 @@
  */
 
 ( function( $ ) {
-	var $body, $window, $sidebar, adminbarOffset, top = false,
-	    bottom = false, windowWidth, windowHeight, lastWindowPos = 0,
-	    topOffset = 0, bodyHeight, sidebarHeight, resizeTimer,
-	    secondary, button;
+	var $body, $window, $sidebar, resizeTimer,
+		secondary, button;
 
 	function initMainNavigation( container ) {
 		// Add dropdown toggle that display child menu items.
@@ -96,71 +94,32 @@
 	}
 
 	// Sidebar scrolling.
-	function resize() {
-		windowWidth = $window.width();
-
-		if ( 955 > windowWidth ) {
-			top = bottom = false;
-			$sidebar.removeAttr( 'style' );
-		}
-	}
-
-	function scroll() {
-		var windowPos = $window.scrollTop();
-
-		if ( 955 > windowWidth ) {
-			return;
-		}
-
-		sidebarHeight = $sidebar.height();
-		windowHeight  = $window.height();
-		bodyHeight    = $body.height();
-
-		if ( sidebarHeight + adminbarOffset > windowHeight ) {
-			if ( windowPos > lastWindowPos ) {
-				if ( top ) {
-					top = false;
-					topOffset = ( $sidebar.offset().top > 0 ) ? $sidebar.offset().top - adminbarOffset : 0;
-					$sidebar.attr( 'style', 'top: ' + topOffset + 'px;' );
-				} else if ( ! bottom && windowPos + windowHeight > sidebarHeight + $sidebar.offset().top && sidebarHeight + adminbarOffset < bodyHeight ) {
-					bottom = true;
-					$sidebar.attr( 'style', 'position: fixed; bottom: 0;' );
-				}
-			} else if ( windowPos < lastWindowPos ) {
-				if ( bottom ) {
-					bottom = false;
-					topOffset = ( $sidebar.offset().top > 0 ) ? $sidebar.offset().top - adminbarOffset : 0;
-					$sidebar.attr( 'style', 'top: ' + topOffset + 'px;' );
-				} else if ( ! top && windowPos + adminbarOffset < $sidebar.offset().top ) {
-					top = true;
-					$sidebar.attr( 'style', 'position: fixed;' );
-				}
-			} else {
-				top = bottom = false;
-				topOffset = ( $sidebar.offset().top > 0 ) ? $sidebar.offset().top - adminbarOffset : 0;
-				$sidebar.attr( 'style', 'top: ' + topOffset + 'px;' );
-			}
-		} else if ( ! top ) {
-			top = true;
-			$sidebar.attr( 'style', 'position: fixed;' );
-		}
-
-		lastWindowPos = windowPos;
-	}
-
 	function resizeAndScroll() {
-		resize();
-		scroll();
+		var windowPos = $window.scrollTop(),
+			windowHeight = $window.height(),
+			sidebarHeight = $sidebar.height(),
+			bodyHeight = $body.height();
+
+		if( 955 < $window.width()
+			&& bodyHeight > sidebarHeight
+			&& ( windowPos + windowHeight ) >= sidebarHeight ) {
+
+			$sidebar.css({
+				position: "fixed",
+				bottom: sidebarHeight > windowHeight ? 0 : 'auto'
+			});
+		} else {
+			$sidebar.css('position', 'relative')
+		}
 	}
 
 	$( document ).ready( function() {
 		$body          = $( document.body );
 		$window        = $( window );
 		$sidebar       = $( '#sidebar' ).first();
-		adminbarOffset = $body.is( '.admin-bar' ) ? $( '#wpadminbar' ).height() : 0;
 
 		$window
-			.on( 'scroll.twentyfifteen', scroll )
+			.on( 'scroll.twentyfifteen', resizeAndScroll )
 			.on( 'load.twentyfifteen', onResizeARIA )
 			.on( 'resize.twentyfifteen', function() {
 				clearTimeout( resizeTimer );
@@ -169,9 +128,7 @@
 			} );
 		$sidebar.on( 'click.twentyfifteen keydown.twentyfifteen', 'button', resizeAndScroll );
 
-		resizeAndScroll();
-
-		for ( var i = 1; i < 6; i++ ) {
+		for ( var i = 0; i < 6; i++ ) {
 			setTimeout( resizeAndScroll, 100 * i );
 		}
 	} );
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 850ed32c83..b061d2df2a 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.3-beta1-46294';
+$wp_version = '5.3-beta1-46308';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.