diff --git a/releases/2.0.0/index.md b/releases/2.0.0/index.md
index c8cf8c9..fec9183 100644
--- a/releases/2.0.0/index.md
+++ b/releases/2.0.0/index.md
@@ -39,5 +39,7 @@ custom_css: releases
 
 * Removed deprecated property: observable:creationTime ([*GitHub Issue 508*](https://github.com/ucoProject/UCO/issues/508))
 * Aligned types:Thread with core:UcoInherentCharacterizationThing ([*GitHub Issue 509*](https://github.com/ucoProject/UCO/issues/509))
+* Designated `observable:ObservablePattern` a subclass of `pattern:Pattern` ([*GitHub Issue 543*](https://github.com/ucoProject/UCO/issues/543))
+
 
 ## Documentation