Index: src/main/java/org/apache/maven/tools/plugin/generator/PluginXdocGenerator.java
===================================================================
--- src/main/java/org/apache/maven/tools/plugin/generator/PluginXdocGenerator.java	(revision 419837)
+++ src/main/java/org/apache/maven/tools/plugin/generator/PluginXdocGenerator.java	(working copy)
@@ -255,7 +255,7 @@
             {
                 String expression = parameter.getExpression();
 
-                if ( expression != null && !expression.startsWith( "${component." ) )
+                if ( expression == null || !expression.startsWith( "${component." ) )
                 {
                     filtered.add( parameter );
                 }