diff --git a/src/main/java/cz/cvut/kbss/study/model/User.java b/src/main/java/cz/cvut/kbss/study/model/User.java
index 8bf94978..baaf644c 100644
--- a/src/main/java/cz/cvut/kbss/study/model/User.java
+++ b/src/main/java/cz/cvut/kbss/study/model/User.java
@@ -56,7 +56,7 @@ public class User implements HasDerivableUri, Serializable {
     @OWLDataProperty(iri = Vocabulary.s_p_created)
     private Date dateCreated;
 
-    //    @ParticipationConstraints(nonEmpty = true)
+    @ParticipationConstraints(nonEmpty = true)
     @OWLObjectProperty(iri = Vocabulary.s_p_is_member_of, fetch = FetchType.EAGER)
     private Institution institution;