diff --git a/logstash-core/src/main/java/org/logstash/config/ir/graph/algorithms/BreadthFirst.java b/logstash-core/src/main/java/org/logstash/config/ir/graph/algorithms/BreadthFirst.java
index 0c16c171614..3a012f0dff0 100644
--- a/logstash-core/src/main/java/org/logstash/config/ir/graph/algorithms/BreadthFirst.java
+++ b/logstash-core/src/main/java/org/logstash/config/ir/graph/algorithms/BreadthFirst.java
@@ -38,7 +38,6 @@ public static BfsResult breadthFirst(Collection<Vertex> roots,
                                         Consumer<Map.Entry<Vertex, Integer>> consumer
                                         ) {
     Map<Vertex, Integer> vertexDistances = new HashMap<>();
-    Map<Vertex, Vertex> vertexParents = new HashMap<>();
 
     Deque<Vertex> queue = new ArrayDeque<>(roots);
     roots.forEach(v -> vertexDistances.put(v, 0));
@@ -55,7 +54,6 @@ public static BfsResult breadthFirst(Collection<Vertex> roots,
         nextVertices.forEach(nextVertex -> {
             if (vertexDistances.get(nextVertex) == null) {
                 vertexDistances.put(nextVertex, currentDistance+1);
-                vertexParents.put(nextVertex, currentVertex);
                 queue.push(nextVertex);
             }
         });