diff --git a/logstash-core/src/main/java/org/logstash/config/ir/graph/algorithms/TopologicalSort.java b/logstash-core/src/main/java/org/logstash/config/ir/graph/algorithms/TopologicalSort.java
index 21b95966c00..b8927fe5351 100644
--- a/logstash-core/src/main/java/org/logstash/config/ir/graph/algorithms/TopologicalSort.java
+++ b/logstash-core/src/main/java/org/logstash/config/ir/graph/algorithms/TopologicalSort.java
@@ -41,8 +41,7 @@ public static List<Vertex> sortVertices(Graph g) throws UnexpectedGraphCycleErro
 
         List<Vertex> sorted = new ArrayList<>(g.getVertices().size());
 
-        Deque<Vertex> pending = new LinkedList<>();
-        pending.addAll(g.getRoots());
+        Deque<Vertex> pending = new LinkedList<>(g.getRoots());
 
         Set<Edge> traversedEdges = new HashSet<>();