diff --git a/src/main/resources/Group.hbm.xml b/src/main/resources/Group.hbm.xml
index e73bee2..41104b5 100644
--- a/src/main/resources/Group.hbm.xml
+++ b/src/main/resources/Group.hbm.xml
@@ -18,7 +18,7 @@
         <property name="uri" column="URI" not-null="true"/>
         <property name="name" column="NAME" not-null="true"/>
         <set name = "requests" cascade="all">
-            <key column = "GID" not-null="false"/>
+            <key column = "GID" not-null="true"/>
             <one-to-many class="Request"/>
         </set>
         <set name = "members"