diff --git a/src/dnslib/node.h b/src/dnslib/node.h
index 9732047721904e1e473f15fd88ffff724785047b..1a48d923847a22667f0c2a073833b67b2a65aa0e 100644
--- a/src/dnslib/node.h
+++ b/src/dnslib/node.h
@@ -56,9 +56,7 @@ dnslib_node_t *dnslib_node_new( dnslib_dname_t *owner, dnslib_node_t *parent );
  * \param rrset RRSet to add.
  *
  * \retval 0 on success.
- * \retval <> 0 on failure.
- *
- * \todo Specify return values according to implementation.
+ * \retval -2 if rrset can not be inserted.
  */
 int dnslib_node_add_rrset( dnslib_node_t *node, dnslib_rrset_t *rrset );
 
diff --git a/src/dnslib/rrset.h b/src/dnslib/rrset.h
index 7565c831ebcbbbd581f0ea4fa304ea729d3f5226..55003c5edd57cb14c9c19f179ea14752ada2f622 100644
--- a/src/dnslib/rrset.h
+++ b/src/dnslib/rrset.h
@@ -79,10 +79,9 @@ dnslib_rrset_t *dnslib_rrset_new( dnslib_dname_t *owner, uint16_t type,
  * \param rdata RDATA to add to the RRSet.
  *
  * \retval 0 if successful.
- * \retval <> 0 if an error occured.
+ * \retval -2 if either rrset or rdata was equal to NULL.
  *
  * \todo Provide some function for comparing RDATAs.
- * \todo Add return values to the comment to reflect the implementation.
  */
 int dnslib_rrset_add_rdata( dnslib_rrset_t *rrset, dnslib_rdata_t *rdata );