diff --git a/src/main/java/cz/cvut/kbss/study/rest/OidcUserController.java b/src/main/java/cz/cvut/kbss/study/rest/OidcUserController.java
index d2388d20..46321dc5 100644
--- a/src/main/java/cz/cvut/kbss/study/rest/OidcUserController.java
+++ b/src/main/java/cz/cvut/kbss/study/rest/OidcUserController.java
@@ -102,7 +102,7 @@ private boolean equals(HasUri entity1, HasUri entity2){
      * @return the URI of the entity or null if entity is null.
      */
     private URI getURI(HasUri entity){
-        return Optional.of(entity).map(HasUri::getUri).orElse(null);
+        return Optional.ofNullable(entity).map(HasUri::getUri).orElse(null);
     }
 
     private List<User> getByInstitution(String institutionKey) {