diff --git a/src/main/java/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java b/src/main/java/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
index 4c5a4f8c..6b573e3c 100644
--- a/src/main/java/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
+++ b/src/main/java/de/dhbwstuttgart/typeinference/unify/model/UnifyPair.java
@@ -81,7 +81,7 @@ public class UnifyPair {
 	}
 	
 	public UnifyPair(UnifyType lhs, UnifyType rhs, PairOperator op, Set<UnifyPair> uni, UnifyPair base) {
-		this(lhs, rhs, op, uni, base, null);
+		this(lhs, rhs, op, uni, base, new HashSet<>());
 	}
 
 	public UnifyPair(UnifyType lhs, UnifyType rhs, PairOperator op, Set<UnifyPair> uni, UnifyPair base, Set<UnifyType> fBounded) {
@@ -95,7 +95,7 @@ public class UnifyPair {
 		substitution = uni;
 		basePair = base;
 		this.location = location;
-		//this.fBounded = fBounded; // what?
+		this.fBounded = fBounded;
 
 		// Caching hashcode
 		hashCode = 17 + 31 * lhs.hashCode() + 31 * rhs.hashCode() + 31 * pairOp.hashCode();