diff --git a/core/user.class.php b/core/user.class.php
index aa9073d1..5d418bce 100644
--- a/core/user.class.php
+++ b/core/user.class.php
@@ -229,7 +229,7 @@ class User {
 			if(!empty($this->email)) {
 				$hash = md5(strtolower($this->email));
 				$s = $config->get_string("avatar_gravatar_size");
-				$d = $config->get_string("avatar_gravatar_default");
+				$d = urlencode($config->get_string("avatar_gravatar_default"));
 				$r = $config->get_string("avatar_gravatar_rating");
 				return "<img class=\"avatar gravatar\" src=\"http://www.gravatar.com/avatar/$hash.jpg?s=$s&d=$d&r=$r\">";
 			}