diff --git a/src/main/org/apache/tools/ant/taskdefs/Ant.java b/src/main/org/apache/tools/ant/taskdefs/Ant.java
index 402737901..f9e98e6e5 100644
--- a/src/main/org/apache/tools/ant/taskdefs/Ant.java
+++ b/src/main/org/apache/tools/ant/taskdefs/Ant.java
@@ -377,6 +377,12 @@ public class Ant extends Task {
         } finally {
             // help the gc
             newProject = null;
+            Enumeration enum = properties.elements();
+            while (enum.hasMoreElements()) {
+                Property p = (Property) enum.nextElement();
+                p.setProject(null);
+            }
+
             if (output != null && out != null) {
                 try {
                     out.close();
diff --git a/src/main/org/apache/tools/ant/taskdefs/Property.java b/src/main/org/apache/tools/ant/taskdefs/Property.java
index dfcc51b55..aadb591d9 100644
--- a/src/main/org/apache/tools/ant/taskdefs/Property.java
+++ b/src/main/org/apache/tools/ant/taskdefs/Property.java
@@ -320,6 +320,10 @@ public class Property extends Task {
      * here is where it is loaded
      */
     public void execute() throws BuildException {
+        if (getProject() == null) {
+            throw new IllegalStateException("project has not been set");
+        }
+
         if (name != null) {
             if (value == null && ref == null) {
                 throw new BuildException("You must specify value, location or "