Index: src/wp-includes/admin-bar.php
===================================================================
--- src/wp-includes/admin-bar.php	(revision 50819)
+++ src/wp-includes/admin-bar.php	(working copy)
@@ -582,7 +582,15 @@
 	foreach ( (array) $wp_admin_bar->user->blogs as $blog ) {
 		switch_to_blog( $blog->userblog_id );
 
-		$blavatar = '<div class="blavatar"></div>';
+		if ( has_site_icon() ) {
+			$blavatar = sprintf(
+				'<img class="blavatar" src="%s" srcset="%s 2x" alt="" width="16" height="16" />',
+				esc_url( get_site_icon_url( 16 ) ),
+				esc_url( get_site_icon_url( 32 ) )
+			);
+		} else {
+			$blavatar = '<div class="blavatar"></div>';
+		}
 
 		$blogname = $blog->blogname;
 
Index: src/wp-includes/css/admin-bar.css
===================================================================
--- src/wp-includes/css/admin-bar.css	(revision 50819)
+++ src/wp-includes/css/admin-bar.css	(working copy)
@@ -517,14 +517,18 @@
 	color: #72aee6;
 }
 
-#wpadminbar .quicklinks li .blavatar:before {
-	content: "\f120";
+#wpadminbar .quicklinks li img.blavatar,
+#wpadminbar .quicklinks li div.blavatar:before {
 	height: 16px;
 	width: 16px;
-	display: inline-block;
 	margin: 0 8px 2px -2px;
 }
 
+#wpadminbar .quicklinks li div.blavatar:before {
+	content: "\f120";
+	display: inline-block;
+}
+
 #wpadminbar #wp-admin-bar-appearance {
 	margin-top: -12px;
 }