diff --git a/AlgebraicDataflowArchitectureModel/models/RefBug.model b/AlgebraicDataflowArchitectureModel/models/RefBug.model
new file mode 100644
index 0000000..e421f6b
--- /dev/null
+++ b/AlgebraicDataflowArchitectureModel/models/RefBug.model
@@ -0,0 +1,19 @@
+init {
+	constant := 10
+	variable := 10
+	ans := 20
+}
+
+channel changeVar {
+	out variable(cur: Int, change(next: Int)) = next
+}
+
+channel changeConst {
+	out constant(const: Int, change(next: Int)) = next
+}
+
+channel calcAns {
+	in variable(curVar: Int, calc(const: Int, nextVar: Int)) = nextVar
+	ref constant(const: Int, calc(const: Int, var: Int))
+	out ans(curAns: Int, calc(const: Int, var: Int)) = var + const
+}
diff --git a/AlgebraicDataflowArchitectureModel/src/models/dataFlowModel/DataTransferChannel.java b/AlgebraicDataflowArchitectureModel/src/models/dataFlowModel/DataTransferChannel.java
index 15e3194..ec3c6f2 100644
--- a/AlgebraicDataflowArchitectureModel/src/models/dataFlowModel/DataTransferChannel.java
+++ b/AlgebraicDataflowArchitectureModel/src/models/dataFlowModel/DataTransferChannel.java
@@ -1,13 +1,12 @@
 package models.dataFlowModel;
 
 import java.util.AbstractMap;
-import java.util.AbstractMap.SimpleEntry;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
 import java.util.Map.Entry;
+import java.util.Set;
 
 import models.algebra.Constant;
 import models.algebra.Expression;
@@ -19,7 +18,9 @@
 import models.algebra.UnificationFailed;
 import models.algebra.ValueUndefined;
 import models.algebra.Variable;
-import models.dataConstraintModel.*;
+import models.dataConstraintModel.Channel;
+import models.dataConstraintModel.ChannelMember;
+import models.dataConstraintModel.ResourcePath;
 
 public class DataTransferChannel extends Channel {
 	protected Set<ChannelMember> inputChannelMembers = null;
@@ -506,11 +507,11 @@
 			Set<Position> substitutedPositionsInMessage = new HashSet<>();
 			Expression messageTerm = referenceMember.getStateTransition().getMessageExpression();
 			Expression curStateTerm = referenceMember.getStateTransition().getCurStateExpression();
-			Expression nextStateTerm = referenceMember.getStateTransition().getNextStateExpression();
+//			Expression nextStateTerm = referenceMember.getStateTransition().getNextStateExpression();
 			HashMap<Position, Variable> messageVars = messageTerm.getVariables();
 			for (Entry<Position, Variable> varEnt: messageVars.entrySet()) {
 				Variable var = varEnt.getValue();
-				if (curStateTerm.getVariables().values().contains(var) || nextStateTerm.getVariables().values().contains(var)) {
+				if (curStateTerm.getVariables().values().contains(var)) {
 					if (messageTerm instanceof Term) {
 						substitutedPositionsInMessage.add(varEnt.getKey());
 					} else if (messageTerm instanceof Variable) {