diff --git a/src/de/dhbwstuttgart/typeinference/unify/Unify.java b/src/de/dhbwstuttgart/typeinference/unify/Unify.java
index 4d727591..71734187 100644
--- a/src/de/dhbwstuttgart/typeinference/unify/Unify.java
+++ b/src/de/dhbwstuttgart/typeinference/unify/Unify.java
@@ -97,7 +97,12 @@ public class Unify {
 			Set<List<Set<UnifyPair>>> cartResult = setOps.cartesianProduct(secondLevelSetList);
 			
 			Set<Set<UnifyPair>> flat = new HashSet<>();
-			cartResult.stream().forEach(x -> flat.addAll(x));
+			for(List<Set<UnifyPair>> s : cartResult) {
+				Set<UnifyPair> flat1 = new HashSet<>();
+				for(Set<UnifyPair> s1 : s)
+					flat1.addAll(s1);
+				flat.add(flat1);
+			}
 			topLevelSets.add(flat);
 		}