diff --git a/wp-includes/formatting.php b/wp-includes/formatting.php
index df1e490750..822f4dd337 100644
--- a/wp-includes/formatting.php
+++ b/wp-includes/formatting.php
@@ -2645,11 +2645,15 @@ function esc_url( $url, $protocols = null, $_context = 'display' ) {
 		$url = str_replace( "'", ''', $url );
 	}
 
-	if ( ! is_array( $protocols ) )
-		$protocols = wp_allowed_protocols();
-	$good_protocol_url = wp_kses_bad_protocol( $url, $protocols );
-	if ( strtolower( $good_protocol_url ) != strtolower( $url ) )
-		return '';
+	if ( '/' === $url[0] ) {
+		$good_protocol_url = $url;
+	} else {
+		if ( ! is_array( $protocols ) )
+			$protocols = wp_allowed_protocols();
+		$good_protocol_url = wp_kses_bad_protocol( $url, $protocols );
+		if ( strtolower( $good_protocol_url ) != strtolower( $url ) )
+			return '';
+	}
 
 	return apply_filters('clean_url', $good_protocol_url, $original_url, $_context);
 }