diff --git a/src/de/dhbwstuttgart/core/JavaTXCompiler.java b/src/de/dhbwstuttgart/core/JavaTXCompiler.java
index f31255e0..23a2750c 100644
--- a/src/de/dhbwstuttgart/core/JavaTXCompiler.java
+++ b/src/de/dhbwstuttgart/core/JavaTXCompiler.java
@@ -126,28 +126,20 @@ public class JavaTXCompiler {
 				
 				xConsSet = xConsSet.stream().map(x -> { 
 					if ((x.getLhsType() instanceof PlaceholderType)) {
-						if (paraTypeVarNames.contains(x.getLhsType().getName()) 
-								&& (!(x.getRhsType() instanceof PlaceholderType) 
-										|| ((x.getRhsType() instanceof PlaceholderType) && !paraTypeVarNames.contains(x.getRhsType().getName()) && !returnTypeVarNames.contains(x.getRhsType().getName())))) {
-							x.setVariance((byte)1);
+						if (paraTypeVarNames.contains(x.getLhsType().getName())) { 
+							((PlaceholderType)x.getLhsType()).setVariance((byte)1);
 						}
-						if (returnTypeVarNames.contains(x.getLhsType().getName()) 
-								&& (!(x.getRhsType() instanceof PlaceholderType) 
-										|| ((x.getRhsType() instanceof PlaceholderType) && !paraTypeVarNames.contains(x.getRhsType().getName()) && !returnTypeVarNames.contains(x.getRhsType().getName())))) {
-							x.setVariance((byte)-1);
+						if (returnTypeVarNames.contains(x.getLhsType().getName())) {
+							((PlaceholderType)x.getLhsType()).setVariance((byte)-1);
 						}
 					}
 					if ((x.getRhsType() instanceof PlaceholderType)) {
-							if (paraTypeVarNames.contains(x.getRhsType().getName()) 
-									&& (!(x.getLhsType() instanceof PlaceholderType) 
-											|| ((x.getLhsType() instanceof PlaceholderType) && !paraTypeVarNames.contains(x.getLhsType().getName()) && !returnTypeVarNames.contains(x.getLhsType().getName())))) {
-								x.setVariance((byte)1);
-							}
-							if (returnTypeVarNames.contains(x.getRhsType().getName()) 
-									&& (!(x.getLhsType() instanceof PlaceholderType) 
-											|| ((x.getLhsType() instanceof PlaceholderType) && !paraTypeVarNames.contains(x.getLhsType().getName()) && !returnTypeVarNames.contains(x.getLhsType().getName())))) {
-								x.setVariance((byte)-1);
-							}	
+						if (paraTypeVarNames.contains(x.getRhsType().getName())) {
+							((PlaceholderType)x.getRhsType()).setVariance((byte)1);
+						}
+						if (returnTypeVarNames.contains(x.getRhsType().getName())) {
+							((PlaceholderType)x.getRhsType()).setVariance((byte)-1);
+						}	
 					}
 					return x;
 				}).collect(Collectors.toCollection(HashSet::new));
diff --git a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
index ec383afe..24f16bc8 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
@@ -314,7 +314,17 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		writeLog("nextSet: " + nextSet.toString());
 		List<Set<UnifyPair>> nextSetasList = oup.sortedCopy(nextSet);//new ArrayList<>(nextSet);
 		Set<Set<UnifyPair>> result = new HashSet<>(); 
-		byte variance = 	nextSetasList.iterator().next().iterator().next().getVariance();	
+		int variance = 0;
+		Optional<Integer> xi = nextSetasList.stream().map(x -> x.stream().filter(y -> y.getLhsType() instanceof PlaceholderType)
+				                                  .filter(z -> ((PlaceholderType)z.getLhsType()).getVariance() != 0)
+				                                  .map(c -> ((PlaceholderType)c.getLhsType()).getVariance())
+				                                  .reduce((a,b)-> a*b))
+												  .filter(d -> d.isPresent())
+												  .map(e -> e.get())
+												  .findAny();
+		if (xi.isPresent()) {
+			variance = xi.get();
+		}		                                                  
 		if (variance == 1 && nextSetasList.size() > 1) {
 			List<Set<UnifyPair>> al = new ArrayList<>(nextSetasList.size());
 			for (int ii = 0; ii <  nextSetasList.size();ii++) {
diff --git a/src/de/dhbwstuttgart/typeinference/unify/model/PlaceholderType.java b/src/de/dhbwstuttgart/typeinference/unify/model/PlaceholderType.java
index 5aab8784..d9fd6699 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/model/PlaceholderType.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/model/PlaceholderType.java
@@ -37,6 +37,15 @@ public final class PlaceholderType extends UnifyType{
 	 */
 	private final boolean IsGenerated;
 	
+	/**
+     * variance shows the variance of the pair
+     * -1: contravariant
+     * 1 covariant
+     * 0 invariant
+     * PL 2018-03-21
+     */
+    private int variance = 0;
+	
 	/**
 	 * Creates a new placeholder type with the specified name.
 	 */
@@ -80,6 +89,14 @@ public final class PlaceholderType extends UnifyType{
 		return IsGenerated;
 	}
 
+	public void setVariance(int v) {
+		variance = v;
+	}
+	
+	public int getVariance() {
+		return variance;
+	}
+	
 	@Override
 	Set<UnifyType> smArg(IFiniteClosure fc) {
 		return fc.smArg(this);
diff --git a/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java b/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
index 780d05a5..e57c5e42 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
@@ -72,6 +72,7 @@ public class UnifyPair {
 		pairOp = op;
 		unifier = uni;
 		basePair = base;
+		this.variance = variance;
 		
 		
 		// Caching hashcode