diff --git a/src/js/_enqueues/admin/post.js b/src/js/_enqueues/admin/post.js
index cc7cab1a72..221850a4ac 100644
--- a/src/js/_enqueues/admin/post.js
+++ b/src/js/_enqueues/admin/post.js
@@ -200,7 +200,7 @@ window.wp = window.wp || {};
 					}
 
 					if ( received.lock_error.avatar_src ) {
-						avatar = $( '<img class="avatar avatar-64 photo" width="64" height="64" alt="" />' ).attr( 'src', received.lock_error.avatar_src.replace( /&amp;/g, '&' ) );
+						avatar = $( '<img class="avatar avatar-64 photo" width="64" height="64" alt="" />' ).attr( 'srcset', received.lock_error.avatar_srcset.replace( /&amp;/g, '&' ) ).attr( 'src', received.lock_error.avatar_src.replace( /&amp;/g, '&' ) );
 						wrap.find('div.post-locked-avatar').empty().append( avatar );
 					}
 
diff --git a/src/wp-admin/includes/misc.php b/src/wp-admin/includes/misc.php
index e0d4ddc5bc..8faab758e5 100644
--- a/src/wp-admin/includes/misc.php
+++ b/src/wp-admin/includes/misc.php
@@ -1050,9 +1050,15 @@ function wp_check_locked_posts( $response, $data, $screen_id ) {
 						'text' => sprintf( __( '%s is currently editing' ), $user->display_name ),
 					);
 
-					$avatar = get_avatar( $user->ID, 18 );
-					if ( $avatar && preg_match( "|src='([^']+)'|", $avatar, $matches ) ) {
-						$send['avatar_src'] = $matches[1];
+					$avatar_url_args = array(
+						'size' => 64
+					);
+					if ( $avatar_url = get_avatar_url( $user->ID, $avatar_url_args ) ) {
+						$send['avatar_src'] = $avatar_url;
+						$send['avatar_srcset'] = sprintf(
+							'%s 2x',
+							esc_attr( get_avatar_url( $user->ID, array_merge( $avatar_url_args, array( 'size' => $avatar_url_args['size'] * 2 ) ) ) )
+						);
 					}
 
 					$checked[ $key ] = $send;
@@ -1100,11 +1106,15 @@ function wp_refresh_post_lock( $response, $data, $screen_id ) {
 				'text' => sprintf( __( '%s has taken over and is currently editing.' ), $user->display_name ),
 			);
 
-			$avatar = get_avatar( $user->ID, 64 );
-			if ( $avatar ) {
-				if ( preg_match( "|src='([^']+)'|", $avatar, $matches ) ) {
-					$error['avatar_src'] = $matches[1];
-				}
+			$avatar_url_args = array(
+				'size' => 64
+			);
+			if ( $avatar_url = get_avatar_url( $user->ID, $avatar_url_args ) ) {
+				$error['avatar_src'] = $avatar_url;
+				$error['avatar_srcset'] = sprintf(
+					'%s 2x',
+					esc_attr( get_avatar_url( $user->ID, array_merge( $avatar_url_args, array( 'size' => $avatar_url_args['size'] * 2 ) ) ) )
+				);
 			}
 
 			$send['lock_error'] = $error;