diff --git a/src/main/org/apache/tools/ant/AntClassLoader.java b/src/main/org/apache/tools/ant/AntClassLoader.java
index 2748865ae..f9dc88dd6 100644
--- a/src/main/org/apache/tools/ant/AntClassLoader.java
+++ b/src/main/org/apache/tools/ant/AntClassLoader.java
@@ -70,7 +70,7 @@ import org.apache.tools.ant.types.Path;
  * @author <a href="mailto:conor@cortexebusiness.com.au">Conor MacNeill</a>
  * @author <a href="mailto:Jesse.Glick@netbeans.com">Jesse Glick</a>
  */
-public class AntClassLoader  extends ClassLoader {
+public class AntClassLoader  extends ClassLoader implements BuildListener {
 
     /**
      * An enumeration of all resources of a given name found within the
@@ -228,6 +228,7 @@ public class AntClassLoader  extends ClassLoader {
      */
     public AntClassLoader(Project project, Path classpath) {
         this.project = project;
+        this.project.addBuildListener(this);
         this.classpath = classpath.concatSystemClasspath("ignore");
     }
 
@@ -839,4 +840,26 @@ public class AntClassLoader  extends ClassLoader {
             return base.loadClass(name);
         }
     }
+
+    public void buildStarted(BuildEvent event) {}
+
+    public void buildFinished(BuildEvent event) {
+        classpath = null;
+        project = null;
+    }
+
+    public void targetStarted(BuildEvent event) {
+    }
+
+    public void targetFinished(BuildEvent event) {
+    }
+
+    public void taskStarted(BuildEvent event) {
+    }
+
+    public void taskFinished(BuildEvent event) {
+    }
+
+    public void messageLogged(BuildEvent event) {
+    }
 }
diff --git a/src/main/org/apache/tools/ant/IntrospectionHelper.java b/src/main/org/apache/tools/ant/IntrospectionHelper.java
index bc99c4a4f..5a3dfd0bb 100644
--- a/src/main/org/apache/tools/ant/IntrospectionHelper.java
+++ b/src/main/org/apache/tools/ant/IntrospectionHelper.java
@@ -68,7 +68,7 @@ import java.util.*;
  *
  * @author <a href="mailto:stefan.bodewig@epost.de">Stefan Bodewig</a>
  */
-public class IntrospectionHelper  {
+public class IntrospectionHelper implements BuildListener {
 
     /**
      * holds the types of the attributes that could be set.
@@ -552,4 +552,20 @@ public class IntrospectionHelper  {
             throws InvocationTargetException, IllegalAccessException, 
                    BuildException;
     }
+
+    public void buildStarted(BuildEvent event) {}
+    public void buildFinished(BuildEvent event) {
+	attributeTypes.clear();
+	attributeSetters.clear();
+	nestedTypes.clear();
+	nestedCreators.clear();
+	addText = null;
+        helpers.clear();
+    }
+
+    public void targetStarted(BuildEvent event) {}
+    public void targetFinished(BuildEvent event) {}
+    public void taskStarted(BuildEvent event) {}
+    public void taskFinished(BuildEvent event) {}
+    public void messageLogged(BuildEvent event) {}
 }
diff --git a/src/main/org/apache/tools/ant/ProjectHelper.java b/src/main/org/apache/tools/ant/ProjectHelper.java
index 02ecdfba6..62bfb2b50 100644
--- a/src/main/org/apache/tools/ant/ProjectHelper.java
+++ b/src/main/org/apache/tools/ant/ProjectHelper.java
@@ -628,6 +628,8 @@ public class ProjectHelper {
         IntrospectionHelper ih = 
             IntrospectionHelper.getHelper(target.getClass());
 
+        project.addBuildListener(ih);
+
         for (int i = 0; i < attrs.getLength(); i++) {
             // reflect these into the target
             String value=replaceProperties(project, attrs.getValue(i),