diff --git a/AlgebraicDataflowArchitectureModel/src/application/editor/stages/DataFlowModelingStage.java b/AlgebraicDataflowArchitectureModel/src/application/editor/stages/DataFlowModelingStage.java
index 48a2ca9..2708810 100644
--- a/AlgebraicDataflowArchitectureModel/src/application/editor/stages/DataFlowModelingStage.java
+++ b/AlgebraicDataflowArchitectureModel/src/application/editor/stages/DataFlowModelingStage.java
@@ -31,8 +31,8 @@
 public class DataFlowModelingStage extends Stage {
 	private HashMap<ResourceNode, mxCell> resNodeToCell = new HashMap<>();
 	private HashMap<DataTransferChannel, mxCell> channelToCell = new HashMap<>();
-	private HashMap<mxCell, ResourceNode> cellToResNode = new HashMap<>();
-	private HashMap<mxCell, DataTransferChannel> cellToChannel = new HashMap<>();
+	private final HashMap<mxCell, ResourceNode> cellToResNode = new HashMap<>();
+	private final HashMap<mxCell, DataTransferChannel> cellToChannel = new HashMap<>();
 	
 	public DataFlowModelingStage(mxGraphComponent graphComponent) {
 		super(graphComponent);