diff --git a/wp-includes/feed.php b/wp-includes/feed.php
index cba5d91a7c..ecb4a25293 100644
--- a/wp-includes/feed.php
+++ b/wp-includes/feed.php
@@ -672,14 +672,7 @@ function get_feed_build_date( $format ) {
 	}
 
 	// Determine the maximum modified time.
-	$max_modified_time = max(
-		array_map(
-			function ( $time ) use ( $format ) {
-				return mysql2date( $format, $time, false );
-			},
-			$modified_times
-		)
-	);
+	$max_modified_time = mysql2date( $format, max( $modified_times ), false );
 
 	/**
 	 * Filters the date the last post or comment in the query was modified.