diff --git a/classpath/avian/SystemClassLoader.java b/classpath/avian/SystemClassLoader.java
index fc566b9c1c..abcf596bd5 100644
--- a/classpath/avian/SystemClassLoader.java
+++ b/classpath/avian/SystemClassLoader.java
@@ -29,7 +29,7 @@ public class SystemClassLoader extends ClassLoader {
 
   protected native Class findClass(String name) throws ClassNotFoundException;
 
-  protected native Class findLoadedClass(String name);
+  protected native Class reallyFindLoadedClass(String name);
 
   private native boolean resourceExists(String name);
 
diff --git a/classpath/java/lang/ClassLoader.java b/classpath/java/lang/ClassLoader.java
index 633c1f64f9..9cb5b0e664 100644
--- a/classpath/java/lang/ClassLoader.java
+++ b/classpath/java/lang/ClassLoader.java
@@ -49,8 +49,10 @@ public abstract class ClassLoader {
     throw new ClassNotFoundException();
   }
 
-  protected Class findLoadedClass(String name) {
-    return null;
+  protected abstract Class reallyFindLoadedClass(String name);
+
+  protected final Class findLoadedClass(String name) {
+    return reallyFindLoadedClass(name);
   }
 
   public Class loadClass(String name) throws ClassNotFoundException {
diff --git a/classpath/java/lang/ThreadGroup.java b/classpath/java/lang/ThreadGroup.java
index 077db46dca..5145f0e865 100644
--- a/classpath/java/lang/ThreadGroup.java
+++ b/classpath/java/lang/ThreadGroup.java
@@ -10,13 +10,20 @@
 
 package java.lang;
 
+import avian.Cell;
+
 public class ThreadGroup implements Thread.UncaughtExceptionHandler {
-  private final ThreadGroup parent;
+  final ThreadGroup parent; // package private for GNU Classpath compatibility
   private final String name;
+  private Cell<ThreadGroup> subgroups;
 
   public ThreadGroup(ThreadGroup parent, String name) {
     this.parent = parent;
     this.name = name;
+
+    synchronized (parent) {
+      parent.subgroups = new Cell(this, subgroups);
+    }
   }
 
   public ThreadGroup(String name) {
@@ -36,4 +43,75 @@ public class ThreadGroup implements Thread.UncaughtExceptionHandler {
       }
     }
   }
+
+  public ThreadGroup getParent() {
+    return parent;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public int activeCount() {
+    int allCount = Thread.activeCount();
+    Thread[] all = new Thread[allCount];
+    allCount = Thread.enumerate(all);
+
+    int count = 0;
+    for (int i = 0; i < allCount; ++i) {
+      if (parentOf(all[i].getThreadGroup())) {
+        ++ count;
+      }
+    }
+
+    return count;
+  }
+
+  public int enumerate(Thread[] threads) {
+    return enumerate(threads, true);
+  }
+
+  public int enumerate(Thread[] threads, boolean recurse) {
+    int allCount = Thread.activeCount();
+    Thread[] all = new Thread[allCount];
+    allCount = Thread.enumerate(all);
+
+    int count = 0;
+    for (int i = 0; i < allCount && count < threads.length; ++i) {
+      Thread t = all[i];
+      ThreadGroup g = t.getThreadGroup();
+      if (g == this || (recurse && parentOf(g))) {
+        threads[count++] = t;
+      }
+    }
+
+    return count;
+  }  
+
+  public boolean parentOf(ThreadGroup g) {
+    for (; g != null; g = g.parent) {
+      if (g == this) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
+  public int enumerate(ThreadGroup[] groups, boolean recurse) {
+    return enumerate(groups, recurse, 0);
+  }
+
+  private int enumerate(ThreadGroup[] groups, boolean recurse, int count) {
+    for (Cell<ThreadGroup> c = subgroups; c != null && count < groups.length;
+         c = c.next)
+    {
+      ThreadGroup g = c.value;
+      groups[count++] = g;
+      if (recurse) {
+        count = g.enumerate(groups, true, count);
+      }
+    }
+    return count;
+  }
 }
diff --git a/classpath/java/lang/reflect/Proxy.java b/classpath/java/lang/reflect/Proxy.java
index 3dd5109565..aca0351217 100644
--- a/classpath/java/lang/reflect/Proxy.java
+++ b/classpath/java/lang/reflect/Proxy.java
@@ -82,6 +82,14 @@ public class Proxy {
     }
   }
 
+  public static boolean isProxyClass(Class c) {
+    return c.getName().startsWith("Proxy-");
+  }
+
+  public static InvocationHandler getInvocationHandler(Object proxy) {
+    return ((Proxy) proxy).h;
+  }
+
   private static void set4(byte[] array, int offset, int v) {
     array[offset    ] = (byte) ((v >>> 24) & 0xFF);
     array[offset + 1] = (byte) ((v >>> 16) & 0xFF);
diff --git a/src/builtin.cpp b/src/builtin.cpp
index ddd900ae25..560f8cc53e 100644
--- a/src/builtin.cpp
+++ b/src/builtin.cpp
@@ -214,7 +214,7 @@ Avian_avian_SystemClassLoader_defineClass
 }
 
 extern "C" JNIEXPORT int64_t JNICALL
-Avian_avian_SystemClassLoader_findLoadedClass
+Avian_avian_SystemClassLoader_reallyFindLoadedClass
 (Thread* t, object, uintptr_t* arguments)
 {
   object name = reinterpret_cast<object>(arguments[1]);
diff --git a/src/machine.cpp b/src/machine.cpp
index e6bb889cbf..03680b8df8 100644
--- a/src/machine.cpp
+++ b/src/machine.cpp
@@ -234,7 +234,7 @@ makeJavaThread(Thread* t, Thread* parent)
   if (parent) {
     group = threadGroup(t, parent->javaThread);
   } else {
-    group = makeThreadGroup(t, 0, 0);
+    group = makeThreadGroup(t, 0, 0, 0);
   }
 
   const unsigned NewState = 0;