diff --git a/AlgebraicDataflowArchitectureModel/src/simulator/Resource.java b/AlgebraicDataflowArchitectureModel/src/simulator/Resource.java
index c88b684..48dad8f 100644
--- a/AlgebraicDataflowArchitectureModel/src/simulator/Resource.java
+++ b/AlgebraicDataflowArchitectureModel/src/simulator/Resource.java
@@ -106,7 +106,9 @@
 	}
 	
 	public Collection<Resource> getChildren() {
-		return getChildrenMap().values();
+		Map<String, Resource> childrenMap = getChildrenMap();
+		if (childrenMap == null) return null;
+		return childrenMap.values();
 	}
 
 	public Map<String, Resource> getChildrenMap() {