diff --git a/src/it/projects/evaluate-model-collections/invoker.properties b/src/it/projects/evaluate-model-collections/invoker.properties
index 64862c9..e9c555f 100644
--- a/src/it/projects/evaluate-model-collections/invoker.properties
+++ b/src/it/projects/evaluate-model-collections/invoker.properties
@@ -16,4 +16,3 @@
 # under the License.
 
 invoker.goals = ${project.groupId}:${project.artifactId}:${project.version}:evaluate
-invoker.maven.version = 4-
diff --git a/src/main/java/org/apache/maven/plugins/help/EvaluateMojo.java b/src/main/java/org/apache/maven/plugins/help/EvaluateMojo.java
index 615b93b..111c756 100644
--- a/src/main/java/org/apache/maven/plugins/help/EvaluateMojo.java
+++ b/src/main/java/org/apache/maven/plugins/help/EvaluateMojo.java
@@ -37,6 +37,7 @@
 import com.thoughtworks.xstream.XStream;
 import com.thoughtworks.xstream.converters.MarshallingContext;
 import com.thoughtworks.xstream.converters.collections.CollectionConverter;
+import com.thoughtworks.xstream.converters.collections.MapConverter;
 import com.thoughtworks.xstream.converters.collections.PropertiesConverter;
 import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
 import org.apache.maven.execution.MavenSession;
@@ -372,6 +373,12 @@ public boolean canConvert(Class type) {
                     return Collection.class.isAssignableFrom(type);
                 }
             });
+            xstream.registerConverter(new MapConverter(xstream.getMapper()) {
+                @Override
+                public boolean canConvert(Class type) {
+                    return Map.class.isAssignableFrom(type);
+                }
+            });
             addAlias(xstream);
 
             // handle Properties a la Maven