diff --git a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
index f8af5dd7..4af7a62c 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
@@ -156,7 +156,9 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		// those pairs are contradictory and the unification is impossible.
 		if(!undefinedPairs.isEmpty()) {
 			writeLog("UndefinedPairs; " + undefinedPairs);
-			return new HashSet<>();
+			Set<Set<UnifyPair>> error = new HashSet<>();
+			error.add(undefinedPairs);
+			return error;
 		}
 		
 		/* Up to here, no cartesian products are calculated.
@@ -310,7 +312,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		int i = 0;
 		byte variance = 	nextSetasList.iterator().next().iterator().next().getVariance();	
 		Set<UnifyPair> a_next = null;
-		if (nextSetasList.iterator().next().iterator().next().getLhsType().getName().equals("A")) 
+		if (nextSetasList.iterator().next().iterator().next().getLhsType().getName().equals("D")) 
 			System.out.print("");
 		if (nextSetasList.size()>1) {
 			if (variance == 1) {
@@ -360,6 +362,10 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 			else {
 				result.addAll(computeCartesianRecursive(elems, remainingSets, eq, fc, parallel)); 
 			}
+			if (result.size() == 1) {
+				System.out.println(result.toString());
+				result.remove(result.iterator().next());
+			}
 			if (!result.isEmpty()) {
 				if (variance == 1) {
 					if (a.iterator().next().getLhsType().getName().equals("WL")) 
diff --git a/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java b/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
index abb7651c..82194363 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
@@ -27,6 +27,8 @@ public class UnifyPair {
 	private PairOperator pairOp;
 	
     private byte variance = 0;
+    
+    private boolean undefinedPair = false;
 	
 	private final int hashCode;
 	
diff --git a/test/javFiles/Matrix.jav b/test/javFiles/Matrix.jav
index e8178ad4..6d73c1fc 100644
--- a/test/javFiles/Matrix.jav
+++ b/test/javFiles/Matrix.jav
@@ -16,6 +16,7 @@ class Matrix extends Vector<Vector<Integer>> {
                 var erg = 0;
                 var k = 0;
                 while(k < v1.size()) {
+                		erg = erg + v1.elementAt(k) * m.elementAt(k).elementAt(j);
                     erg = add(erg, mul1(v1.elementAt(k),
                              m.elementAt(k).elementAt(j)));
                     k++; }