diff --git a/maven-plugin-plugin/src/main/java/org/apache/maven/plugin/plugin/DescriptorGeneratorMojo.java b/maven-plugin-plugin/src/main/java/org/apache/maven/plugin/plugin/DescriptorGeneratorMojo.java
index fb3fb75c0..f289e2158 100644
--- a/maven-plugin-plugin/src/main/java/org/apache/maven/plugin/plugin/DescriptorGeneratorMojo.java
+++ b/maven-plugin-plugin/src/main/java/org/apache/maven/plugin/plugin/DescriptorGeneratorMojo.java
@@ -29,6 +29,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.*;
+import java.util.ArrayList;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -196,7 +197,7 @@ public class DescriptorGeneratorMojo extends AbstractGeneratorMojo {
      * @since 3.5
      */
     @Parameter
-    private List<String> mojoDependencies = null;
+    private final List<String> mojoDependencies = new ArrayList<>();
 
     /**
      * Creates links to existing external javadoc-generated documentation.
@@ -372,7 +373,12 @@ public void generate() throws MojoExecutionException {
             mojoScanner.populatePluginDescriptor(request);
             request.setPluginDescriptor(extendPluginDescriptor(request));
 
-            outputDirectory.mkdirs();
+            if (!outputDirectory.exists()) {
+                if (!outputDirectory.mkdirs()) {
+                    throw new MojoExecutionException(
+                            "Could not create output directory: " + outputDirectory.getAbsolutePath());
+                }
+            }
 
             PluginDescriptorFilesGenerator pluginDescriptorGenerator = new PluginDescriptorFilesGenerator();
             pluginDescriptorGenerator.execute(outputDirectory, request);