diff --git a/active-object/README.md b/active-object/README.md
index 48db671e4..6e974034a 100644
--- a/active-object/README.md
+++ b/active-object/README.md
@@ -123,4 +123,4 @@ Now, we can create multiple creatures such as Orcs, tell them to eat and roam an
 
 ## Class diagram
 
-![alt text](./etc/active-object.urm.PNG "Active Object class diagram")
+![alt text](./etc/active-object.urm.png "Active Object class diagram")
diff --git a/active-object/etc/active-object.urm.PNG b/active-object/etc/active-object.urm.png
similarity index 100%
rename from active-object/etc/active-object.urm.PNG
rename to active-object/etc/active-object.urm.png