diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index 6a0af16a8b..ad271c2ab8 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -4945,9 +4945,9 @@ function wp_resolve_post_date( $post_date = '', $post_date_gmt = '' ) {
 	}
 
 	// Validate the date.
-	$month = substr( $post_date, 5, 2 );
-	$day   = substr( $post_date, 8, 2 );
-	$year  = substr( $post_date, 0, 4 );
+	$month = (int) substr( $post_date, 5, 2 );
+	$day   = (int) substr( $post_date, 8, 2 );
+	$year  = (int) substr( $post_date, 0, 4 );
 
 	$valid_date = wp_checkdate( $month, $day, $year, $post_date );