diff --git a/maven-project/src/main/java/org/apache/maven/project/DefaultMavenProjectBuilder.java b/maven-project/src/main/java/org/apache/maven/project/DefaultMavenProjectBuilder.java
index d9fb1e1d8c..18bb195d8b 100644
--- a/maven-project/src/main/java/org/apache/maven/project/DefaultMavenProjectBuilder.java
+++ b/maven-project/src/main/java/org/apache/maven/project/DefaultMavenProjectBuilder.java
@@ -162,6 +162,11 @@ public class DefaultMavenProjectBuilder
 
     public static final String MAVEN_MODEL_VERSION = "4.0.0";
 
+    //DO NOT USE, it is here only for backward compatibility reasons. The existing 
+    // maven-assembly-plugin (2.2-beta-1) is accessing it via reflection.
+    private Map processedProjectCache = new HashMap();
+    
+
     public void initialize()
     {
         modelReader = new MavenXpp3Reader();