diff --git a/src/wp-admin/includes/upgrade.php b/src/wp-admin/includes/upgrade.php
index 598635067f..8515113f78 100644
--- a/src/wp-admin/includes/upgrade.php
+++ b/src/wp-admin/includes/upgrade.php
@@ -1461,7 +1461,7 @@ function upgrade_430() {
 			);
 		}
 
-		if ( 'byte' !== $content_length['type'] ) {
+		if ( 'byte' !== $content_length['type'] || 0 === $content_length['length'] ) {
 			// Sites with malformed DB schemas are on their own.
 			return;
 		}