diff --git a/src/main/java/MaximumWeightBipartiteAuctionMatching.java b/src/main/java/MaximumWeightBipartiteAuctionMatching.java
index b5ebd84..7b95295 100644
--- a/src/main/java/MaximumWeightBipartiteAuctionMatching.java
+++ b/src/main/java/MaximumWeightBipartiteAuctionMatching.java
@@ -16,8 +16,8 @@ public class MaximumWeightBipartiteAuctionMatching<V, E> implements MatchingAlgo
     private final Set<V> partition1;
     private final Set<V> partition2;
     private final BigDecimal delta;
-    private Set<E> matching;
-    private BigDecimal matchingWeight;
+    private final Set<E> matching;
+    private final BigDecimal matchingWeight;
 
     public MaximumWeightBipartiteAuctionMatching(Graph<V, E> graph, Set<V> partition1, Set<V> partition2) {
         this.graph = GraphTests.requireUndirected(graph);