diff --git a/src/wp-admin/includes/ajax-actions.php b/src/wp-admin/includes/ajax-actions.php
index 29cac97917..53fd8671d1 100644
--- a/src/wp-admin/includes/ajax-actions.php
+++ b/src/wp-admin/includes/ajax-actions.php
@@ -3463,6 +3463,7 @@ function wp_ajax_update_theme() {
 	$status     = array(
 		'update'     => 'theme',
 		'slug'       => $stylesheet,
+		'oldVersion' => '',
 		'newVersion' => '',
 	);
 
@@ -3471,6 +3472,11 @@ function wp_ajax_update_theme() {
 		wp_send_json_error( $status );
 	}
 
+	$theme = wp_get_theme( $stylesheet );
+	if ( $theme->exists() ) {
+		$status['oldVersion'] = $theme->get( 'Version' );
+	}
+
 	include_once( ABSPATH . 'wp-admin/includes/class-wp-upgrader.php' );
 
 	$current = get_site_transient( 'update_themes' );
@@ -3502,7 +3508,7 @@ function wp_ajax_update_theme() {
 		}
 
 		$theme = wp_get_theme( $stylesheet );
-		if ( $theme->get( 'Version' ) ) {
+		if ( $theme->exists() ) {
 			$status['newVersion'] = $theme->get( 'Version' );
 		}