diff --git a/initializr-web/src/main/java/io/spring/initializr/web/project/ProjectGenerationInvoker.java b/initializr-web/src/main/java/io/spring/initializr/web/project/ProjectGenerationInvoker.java
index 7f159f94..52e5f88b 100644
--- a/initializr-web/src/main/java/io/spring/initializr/web/project/ProjectGenerationInvoker.java
+++ b/initializr-web/src/main/java/io/spring/initializr/web/project/ProjectGenerationInvoker.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -56,7 +56,7 @@ public class ProjectGenerationInvoker<R extends ProjectRequest> {
 
 	private final ProjectRequestToDescriptionConverter<R> requestConverter;
 
-	private transient Map<Path, List<Path>> temporaryFiles = new ConcurrentHashMap<>();
+	private final transient Map<Path, List<Path>> temporaryFiles = new ConcurrentHashMap<>();
 
 	public ProjectGenerationInvoker(ApplicationContext parentApplicationContext,
 			ProjectRequestToDescriptionConverter<R> requestConverter) {
@@ -144,10 +144,7 @@ public class ProjectGenerationInvoker<R extends ProjectRequest> {
 
 	private void addTempFile(Path group, Path file) {
 		this.temporaryFiles.compute(group, (path, paths) -> {
-			List<Path> newPaths = paths;
-			if (newPaths == null) {
-				newPaths = new ArrayList<>();
-			}
+			List<Path> newPaths = (paths != null) ? paths : new ArrayList<>();
 			newPaths.add(file);
 			return newPaths;
 		});