diff --git a/wp-admin/themes.php b/wp-admin/themes.php
index 4f31f806ca..a3f6dde7c9 100644
--- a/wp-admin/themes.php
+++ b/wp-admin/themes.php
@@ -69,7 +69,7 @@ foreach ($theme_names as $theme_name) {
 	$author = $themes[$theme_name]['Author'];
 	$screenshot = $themes[$theme_name]['Screenshot'];
 	$stylesheet_dir = $themes[$theme_name]['Stylesheet Dir'];
-	$activate_link = wp_nonce_url("themes.php?action=activate&template=$template&stylesheet=$stylesheet", 'switch-theme_' . $template);
+	$activate_link = wp_nonce_url("themes.php?action=activate&template=".urlencode($template)."&stylesheet=".urlencode($stylesheet), 'switch-theme_' . $template);
 ?>
 <div class="available-theme">
 <h3><a href="<?php echo $activate_link; ?>"><?php echo $title; ?></a></h3>