diff --git a/server/src/main/java/org/elasticsearch/action/bulk/TransportBulkAction.java b/server/src/main/java/org/elasticsearch/action/bulk/TransportBulkAction.java
index c849b0a8181ae..3fd9c073485e3 100644
--- a/server/src/main/java/org/elasticsearch/action/bulk/TransportBulkAction.java
+++ b/server/src/main/java/org/elasticsearch/action/bulk/TransportBulkAction.java
@@ -296,7 +296,6 @@ protected void doRun() {
 
     protected void doInternalExecute(Task task, BulkRequest bulkRequest, String executorName, ActionListener<BulkResponse> listener) {
         final long startTime = relativeTime();
-        final AtomicArray<BulkItemResponse> responses = new AtomicArray<>(bulkRequest.requests.size());
 
         boolean hasIndexRequestsWithPipelines = false;
         final Metadata metadata = clusterService.state().getMetadata();
@@ -364,7 +363,7 @@ protected void doInternalExecute(Task task, BulkRequest bulkRequest, String exec
         }
 
         // Step 3: create all the indices that are missing, if there are any missing. start the bulk after all the creates come back.
-        indexData(task, bulkRequest, executorName, listener, responses, autoCreateIndices, indicesThatCannotBeCreated, startTime);
+        indexData(task, bulkRequest, executorName, listener, autoCreateIndices, indicesThatCannotBeCreated, startTime);
     }
 
     protected void indexData(
@@ -372,11 +371,11 @@ protected void indexData(
         BulkRequest bulkRequest,
         String executorName,
         ActionListener<BulkResponse> listener,
-        AtomicArray<BulkItemResponse> responses,
         Set<String> autoCreateIndices,
         Map<String, IndexNotFoundException> indicesThatCannotBeCreated,
         long startTime
     ) {
+        final AtomicArray<BulkItemResponse> responses = new AtomicArray<>(bulkRequest.requests.size());
         if (autoCreateIndices.isEmpty()) {
             executeBulk(task, bulkRequest, startTime, listener, executorName, responses, indicesThatCannotBeCreated);
         } else {
diff --git a/server/src/main/java/org/elasticsearch/action/bulk/TransportSimulateBulkAction.java b/server/src/main/java/org/elasticsearch/action/bulk/TransportSimulateBulkAction.java
index c4352e23abe0c..f26bc28ee3b8a 100644
--- a/server/src/main/java/org/elasticsearch/action/bulk/TransportSimulateBulkAction.java
+++ b/server/src/main/java/org/elasticsearch/action/bulk/TransportSimulateBulkAction.java
@@ -64,13 +64,14 @@ protected void indexData(
         BulkRequest bulkRequest,
         String executorName,
         ActionListener<BulkResponse> listener,
-        AtomicArray<BulkItemResponse> responses,
         Set<String> autoCreateIndices,
         Map<String, IndexNotFoundException> indicesThatCannotBeCreated,
         long startTime
     ) {
+        final AtomicArray<BulkItemResponse> responses = new AtomicArray<>(bulkRequest.requests.size());
         for (int i = 0; i < bulkRequest.requests.size(); i++) {
             DocWriteRequest<?> request = bulkRequest.requests.get(i);
+            assert request instanceof IndexRequest; // This action is only ever called with IndexRequests
             responses.set(
                 i,
                 BulkItemResponse.success(
diff --git a/server/src/main/java/org/elasticsearch/action/ingest/SimulateIndexResponse.java b/server/src/main/java/org/elasticsearch/action/ingest/SimulateIndexResponse.java
index 118027b117b2d..6e5be05e0374d 100644
--- a/server/src/main/java/org/elasticsearch/action/ingest/SimulateIndexResponse.java
+++ b/server/src/main/java/org/elasticsearch/action/ingest/SimulateIndexResponse.java
@@ -50,6 +50,7 @@ public SimulateIndexResponse(String index, BytesReference source, XContentType s
     public XContentBuilder innerToXContent(XContentBuilder builder, Params params) throws IOException {
         builder.field("_index", getShardId().getIndexName());
         builder.field("_source", XContentHelper.convertToMap(source, false, sourceXContentType).v2());
+        assert executedPipelines != null; // This ought to never be null because we always ask to list pipelines in simulate mode
         builder.array("executed_pipelines", executedPipelines.toArray());
         return builder;
     }
diff --git a/server/src/test/java/org/elasticsearch/ingest/IngestServiceTests.java b/server/src/test/java/org/elasticsearch/ingest/IngestServiceTests.java
index 3b114cf0a618e..f8aa3b9431081 100644
--- a/server/src/test/java/org/elasticsearch/ingest/IngestServiceTests.java
+++ b/server/src/test/java/org/elasticsearch/ingest/IngestServiceTests.java
@@ -2604,12 +2604,32 @@ private static IngestService createWithProcessors(
         ThreadPool threadPool = mock(ThreadPool.class);
         when(threadPool.generic()).thenReturn(EsExecutors.DIRECT_EXECUTOR_SERVICE);
         when(threadPool.executor(anyString())).thenReturn(EsExecutors.DIRECT_EXECUTOR_SERVICE);
-        return new IngestService(mock(ClusterService.class), threadPool, null, null, null, List.of(new IngestPlugin() {
-            @Override
-            public Map<String, Processor.Factory> getProcessors(final Processor.Parameters parameters) {
-                return processors;
-            }
-        }), client, null, documentParsingObserverSupplier);
+        IngestService ingestService = new IngestService(
+            mock(ClusterService.class),
+            threadPool,
+            null,
+            null,
+            null,
+            List.of(new IngestPlugin() {
+                @Override
+                public Map<String, Processor.Factory> getProcessors(final Processor.Parameters parameters) {
+                    return processors;
+                }
+            }),
+            client,
+            null,
+            documentParsingObserverSupplier
+        );
+        if (randomBoolean()) {
+            /*
+             * Testing the copy constructor directly is difficult because there is no equals() method in IngestService, but there is a lot
+             * of private internal state. Here we use the copy constructor half the time in all of the unit tests, with the assumption that
+             * if none of our tests observe any difference then the copy constructor is working as expected.
+             */
+            return new IngestService(ingestService);
+        } else {
+            return ingestService;
+        }
     }
 
     private CompoundProcessor mockCompoundProcessor() {