diff --git a/capellambse_context_diagrams/collectors/realization_view.py b/capellambse_context_diagrams/collectors/realization_view.py
index a6bdc0d5..26f0d694 100644
--- a/capellambse_context_diagrams/collectors/realization_view.py
+++ b/capellambse_context_diagrams/collectors/realization_view.py
@@ -99,6 +99,7 @@ def collector(
 
                     if (
                         source is not None
+                        and source.owner is not None
                         and source.owner.uuid in children
                         and owner.uuid in children
                     ):