diff --git a/wp-admin/includes/update-core.php b/wp-admin/includes/update-core.php
index 05b9a3a99d..8c5cd28c7a 100644
--- a/wp-admin/includes/update-core.php
+++ b/wp-admin/includes/update-core.php
@@ -894,7 +894,8 @@ function update_core($from, $to) {
 	do_action( '_core_updated_successfully', $wp_version );
 
 	// Clear the option that blocks auto updates after failures, now that we've been successful.
-	delete_site_option( 'auto_core_update_failed' );
+	if ( function_exists( 'delete_site_option' ) )
+		delete_site_option( 'auto_core_update_failed' );
 
 	return $wp_version;
 }