diff --git a/wp-includes/theme.php b/wp-includes/theme.php
index bf10a04386..266c31add1 100644
--- a/wp-includes/theme.php
+++ b/wp-includes/theme.php
@@ -180,6 +180,7 @@ function get_themes() {
 		$template    = $theme_data['Template'];
 		$stylesheet  = dirname($theme_file);
 
+		$screenshot = false;
 		foreach ( array('png', 'gif', 'jpg', 'jpeg') as $ext ) {
 			if (file_exists("$theme_root/$stylesheet/screenshot.$ext")) {
 				$screenshot = "screenshot.$ext";