diff --git a/onyx/include/common/Theme.class.php b/onyx/include/common/Theme.class.php
index c155fcb7..1d286add 100644
--- a/onyx/include/common/Theme.class.php
+++ b/onyx/include/common/Theme.class.php
@@ -74,7 +74,7 @@ class Theme
 
   function get_name_url()
   {
-    return urlencode($this->name);
+    return preg_replace("#[^a-zA-Z0-9_]#", "_", $this->name);
   }
 
   function get_id()