diff --git a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
index 0ac9fe638..69caef2c0 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/TypeUnifyTask.java
@@ -352,7 +352,7 @@ public class TypeUnifyTask extends RecursiveTask<Set<Set<UnifyPair>>>  {
 		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))
+				                                  .reduce((a,b)-> {if (a==b) return a; else return 0; }))
 												  .filter(d -> d.isPresent())
 												  .map(e -> e.get())
 												  .findAny();