diff --git a/src/main/java/eu/mulk/mulkcms2/benki/accesscontrol/Role.java b/src/main/java/eu/mulk/mulkcms2/benki/accesscontrol/Role.java
index b3efeb9..7c0db71 100644
--- a/src/main/java/eu/mulk/mulkcms2/benki/accesscontrol/Role.java
+++ b/src/main/java/eu/mulk/mulkcms2/benki/accesscontrol/Role.java
@@ -69,7 +69,7 @@
   public User owningUsers;
 
   @ManyToMany(mappedBy = "effectiveRoles", fetch = FetchType.LAZY)
-  public Collection<User> effectiveUsers;
+  public Set<User> effectiveUsers;
 
   @ElementCollection(fetch = FetchType.LAZY)
   @CollectionTable(name = "role_tags", schema = "benki", joinColumns = @JoinColumn(name = "role"))
diff --git a/src/main/java/eu/mulk/mulkcms2/benki/users/User.java b/src/main/java/eu/mulk/mulkcms2/benki/users/User.java
index 72a63f6..3e6559c 100644
--- a/src/main/java/eu/mulk/mulkcms2/benki/users/User.java
+++ b/src/main/java/eu/mulk/mulkcms2/benki/users/User.java
@@ -111,7 +111,7 @@
   public Collection<WikiPageRevision> wikiPageRevisions;
 
   @ManyToMany(mappedBy = "visibleTo", fetch = FetchType.LAZY)
-  public Collection<Post> visiblePosts;
+  public Set<Post> visiblePosts;
 
   @ManyToMany(fetch = FetchType.LAZY)
   @JoinTable(