diff --git a/src/main/org/apache/tools/ant/IntrospectionHelper.java b/src/main/org/apache/tools/ant/IntrospectionHelper.java
index 7b5c44d85..590828d68 100644
--- a/src/main/org/apache/tools/ant/IntrospectionHelper.java
+++ b/src/main/org/apache/tools/ant/IntrospectionHelper.java
@@ -310,12 +310,7 @@ public final class IntrospectionHelper implements BuildListener {
      * @return a helper for the specified class
      */
     public static synchronized IntrospectionHelper getHelper(Class c) {
-        IntrospectionHelper ih = (IntrospectionHelper) helpers.get(c);
-        if (ih == null) {
-            ih = new IntrospectionHelper(c);
-            helpers.put(c, ih);
-        }
-        return ih;
+        return getHelper(null, c);
     }
 
     /**
@@ -332,9 +327,19 @@ public final class IntrospectionHelper implements BuildListener {
      * @return a helper for the specified class
      */
     public static IntrospectionHelper getHelper(Project p, Class c) {
-        IntrospectionHelper ih = getHelper(c);
-        // Cleanup at end of project
-        p.addBuildListener(ih);
+        IntrospectionHelper ih = (IntrospectionHelper) helpers.get(c);
+        if (ih == null) {
+            ih = new IntrospectionHelper(c);
+            if (p != null) {
+                // #30162: do *not* cache this if there is no project, as we
+                // cannot guarantee that the cache will be cleared.
+                helpers.put(c, ih);
+            }
+        }
+        if (p != null) {
+            // Cleanup at end of project
+            p.addBuildListener(ih);
+        }
         return ih;
     }
 
diff --git a/src/main/org/apache/tools/ant/ProjectHelper.java b/src/main/org/apache/tools/ant/ProjectHelper.java
index 15ae624eb..5e0d515ce 100644
--- a/src/main/org/apache/tools/ant/ProjectHelper.java
+++ b/src/main/org/apache/tools/ant/ProjectHelper.java
@@ -304,9 +304,7 @@ public class ProjectHelper {
         }
 
         IntrospectionHelper ih =
-            IntrospectionHelper.getHelper(target.getClass());
-
-        project.addBuildListener(ih);
+            IntrospectionHelper.getHelper(project, target.getClass());
 
         for (int i = 0; i < attrs.getLength(); i++) {
             // reflect these into the target
@@ -368,7 +366,7 @@ public class ProjectHelper {
             target = ((TypeAdapter) target).getProxy();
         }
 
-        IntrospectionHelper.getHelper(target.getClass()).addText(project,
+        IntrospectionHelper.getHelper(project, target.getClass()).addText(project,
             target, text);
     }
 
@@ -388,7 +386,7 @@ public class ProjectHelper {
     public static void storeChild(Project project, Object parent,
          Object child, String tag) {
         IntrospectionHelper ih
-            = IntrospectionHelper.getHelper(parent.getClass());
+            = IntrospectionHelper.getHelper(project, parent.getClass());
         ih.storeElement(project, parent, child, tag);
     }
 
diff --git a/src/main/org/apache/tools/ant/UnknownElement.java b/src/main/org/apache/tools/ant/UnknownElement.java
index 9a0165376..65687cdcb 100644
--- a/src/main/org/apache/tools/ant/UnknownElement.java
+++ b/src/main/org/apache/tools/ant/UnknownElement.java
@@ -320,7 +320,7 @@ public class UnknownElement extends Task {
 
         String parentUri = getNamespace();
         Class parentClass = parent.getClass();
-        IntrospectionHelper ih = IntrospectionHelper.getHelper(parentClass);
+        IntrospectionHelper ih = IntrospectionHelper.getHelper(getProject(), parentClass);
 
 
         if (children != null) {
diff --git a/src/main/org/apache/tools/ant/helper/ProjectHelperImpl.java b/src/main/org/apache/tools/ant/helper/ProjectHelperImpl.java
index 19cc2fac4..02505de65 100644
--- a/src/main/org/apache/tools/ant/helper/ProjectHelperImpl.java
+++ b/src/main/org/apache/tools/ant/helper/ProjectHelperImpl.java
@@ -863,7 +863,7 @@ public class ProjectHelperImpl extends ProjectHelper {
         public void init(String propType, AttributeList attrs) throws SAXParseException {
             Class parentClass = parent.getClass();
             IntrospectionHelper ih =
-                IntrospectionHelper.getHelper(parentClass);
+                IntrospectionHelper.getHelper(helperImpl.project, parentClass);
 
             try {
                 String elementName = propType.toLowerCase(Locale.US);
diff --git a/src/main/org/apache/tools/ant/taskdefs/AntStructure.java b/src/main/org/apache/tools/ant/taskdefs/AntStructure.java
index 14aefe933..41c07a4c7 100644
--- a/src/main/org/apache/tools/ant/taskdefs/AntStructure.java
+++ b/src/main/org/apache/tools/ant/taskdefs/AntStructure.java
@@ -200,7 +200,7 @@ public class AntStructure extends Task {
 
         IntrospectionHelper ih = null;
         try {
-            ih = IntrospectionHelper.getHelper(element);
+            ih = IntrospectionHelper.getHelper(getProject(), element);
         } catch (Throwable t) {
             /*
              * XXX - failed to load the class properly.