Index: main/maven-plugin/src/main/java/hudson/maven/MavenBuild.java
===================================================================
--- main/maven-plugin/src/main/java/hudson/maven/MavenBuild.java	(revision 21942)
+++ main/maven-plugin/src/main/java/hudson/maven/MavenBuild.java	(working copy)
@@ -478,7 +462,7 @@
 
         @Override
         protected Lease decideWorkspace(Node n, WorkspaceList wsl) throws InterruptedException, IOException {
-            return wsl.allocate(getParentBuild().getModuleRoot().child(getProject().getRelativePath()));
+            return wsl.allocate(getModuleSetBuild().getModuleRoot().child(getProject().getRelativePath()));
         }
 
         protected Result doRun(BuildListener listener) throws Exception {