Index: src/wp-content/themes/twentyfifteen/functions.php
===================================================================
--- src/wp-content/themes/twentyfifteen/functions.php	(revision 29997)
+++ src/wp-content/themes/twentyfifteen/functions.php	(working copy)
@@ -209,6 +209,8 @@
 
 	wp_enqueue_script( 'twentyfifteen-skip-link-focus-fix', get_template_directory_uri() . '/js/skip-link-focus-fix.js', array(), '20141010', true );
 
+	wp_enqueue_script( 'twentyfifteen-scroll', get_template_directory_uri() . '/js/scroll.js', array( 'jquery' ), '20141010', true );
+
 	if ( is_singular() && comments_open() && get_option( 'thread_comments' ) ) {
 		wp_enqueue_script( 'comment-reply' );
 	}
Index: src/wp-content/themes/twentyfifteen/js/scroll.js
===================================================================
--- src/wp-content/themes/twentyfifteen/js/scroll.js	(revision 0)
+++ src/wp-content/themes/twentyfifteen/js/scroll.js	(revision 0)
@@ -0,0 +1,25 @@
+jQuery( document ).ready( function ( $ ) {
+		
+	var window_height = $( window ).height();
+	var sidebar_scrollheight = $( '#sidebar' )[0].scrollHeight;
+
+	if( $( '#content' ).height() < window_height && sidebar_scrollheight > window_height ) {
+		$( '#content' ).height( $( '#sidebar' ).height() );
+	}
+
+	var content_scrollheight = $( '#content' )[0].scrollHeight;
+	var ratio = sidebar_scrollheight / content_scrollheight;
+	var offset = content_scrollheight - window_height;
+	var multiplier = content_scrollheight / offset;
+
+	if( $( window ).width() > 967 ) {
+		$( '#sidebar' ).css( 'overflow', 'hidden' );
+		if( sidebar_scrollheight > window_height ) {
+			$( window ).scroll( function() {
+				var content_position = $( window ).scrollTop();
+				var sidebar_position = ( content_position >= 0 ? Math.round( content_position * ratio * multiplier ) : 0 );
+				$( '#sidebar' ).scrollTop( Math.abs( sidebar_position ) );
+			} );
+		}
+	}
+} );
\ No newline at end of file