diff --git a/include/stundenplan.class.php b/include/stundenplan.class.php
index 266571b9e..4e2ce85fc 100644
--- a/include/stundenplan.class.php
+++ b/include/stundenplan.class.php
@@ -262,9 +262,9 @@ class stundenplan extends basis_db
 	public function getStunden($lehreinheit_id)
 	{
 
-		$qry = 'SELECT count(*) AS stunden '
+		$qry = 'SELECT count(*) as stunden FROM (SELECT lehreinheit_id, datum, stunde '
 				. 'FROM lehre.tbl_stundenplan '
-				. 'WHERE lehreinheit_id = ' . $this->db_add_param($lehreinheit_id);
+				. 'WHERE lehreinheit_id = ' . $this->db_add_param($lehreinheit_id).' GROUP by lehreinheit_id, datum, stunde) as a';
 
 		$result = $this->db_query($qry);