diff --git a/README.html b/README.html
index 9ba601e8..949a61ed 100644
--- a/README.html
+++ b/README.html
@@ -977,6 +977,7 @@ Files are no longer hosted at LuaForge.
 <li>Fix return value for table.remove() and table.insert() (fixes issue #39)</li>
 <li>Fix aliasing issue for some multiple assignments from varargs return values (fixes issue #38)</li>
 <li>Let os.getenv() return System.getenv() values first for JSE, then fall back to properties (fixes issue #25)</li>
+<li>Improve collection of orphaned coroutines when yielding from debug hook functions.</li>
 
 </ul></td></tr>
 </table></td></tr></table>
diff --git a/src/core/org/luaj/vm2/LuaThread.java b/src/core/org/luaj/vm2/LuaThread.java
index 1575a600..2286d3c7 100644
--- a/src/core/org/luaj/vm2/LuaThread.java
+++ b/src/core/org/luaj/vm2/LuaThread.java
@@ -63,10 +63,14 @@ public class LuaThread extends LuaValue {
 
 	public static int coroutine_count = 0;
 
-	/** Interval at which to check for lua threads that are no longer referenced. 
-	 * This can be changed by Java startup code if desired.
+	/** Polling interval, in milliseconds, which each thread uses while waiting to
+	 * return from a yielded state to check if the lua threads is no longer
+	 * referenced and therefore should be garbage collected.  
+	 * A short polling interval for many threads will consume server resources. 
+	 * Orphaned threads cannot be detected and collected unless garbage
+	 * collection is run.  This can be changed by Java startup code if desired.
 	 */
-	static long thread_orphan_check_interval = 30000;
+	public static long thread_orphan_check_interval = 5000;
 	
 	public static final int STATUS_INITIAL       = 0;
 	public static final int STATUS_SUSPENDED     = 1;
@@ -83,12 +87,9 @@ public class LuaThread extends LuaValue {
 	public final State state;
 
 	public static final int        MAX_CALLSTACK = 256;
-	
-	/** Interval to check for LuaThread dereferencing.  */
-	public static int GC_INTERVAL = 30000;
 
 	/** Thread-local used by DebugLib to store debugging state. 
-	 * This is ano opaque value that should not be modified by applications. */
+	 * This is an opaque value that should not be modified by applications. */
 	public Object callstack;
 
 	public final Globals globals;
@@ -244,6 +245,15 @@ public class LuaThread extends LuaValue {
 				this.result = LuaValue.NONE;
 			}
 		}
+
+		public synchronized void set_inhook(boolean value) {
+			LuaThread t = (LuaThread) this.lua_thread.get();
+			if (t == null) {
+				this.status = STATUS_DEAD;
+				throw new OrphanedThread();
+			}
+			t.inhook = value;
+		}
 	}
 		
 }
diff --git a/src/core/org/luaj/vm2/lib/CoroutineLib.java b/src/core/org/luaj/vm2/lib/CoroutineLib.java
index 8790c602..f17e063c 100644
--- a/src/core/org/luaj/vm2/lib/CoroutineLib.java
+++ b/src/core/org/luaj/vm2/lib/CoroutineLib.java
@@ -62,8 +62,6 @@ import org.luaj.vm2.Varargs;
  */
 public class CoroutineLib extends TwoArgFunction {
 
-	static long thread_orphan_check_interval = 30000;
-
 	static int coroutine_count = 0;
 
 	Globals globals;
diff --git a/src/core/org/luaj/vm2/lib/DebugLib.java b/src/core/org/luaj/vm2/lib/DebugLib.java
index 17001b3a..f78cb5b0 100644
--- a/src/core/org/luaj/vm2/lib/DebugLib.java
+++ b/src/core/org/luaj/vm2/lib/DebugLib.java
@@ -388,61 +388,55 @@ public class DebugLib extends TwoArgFunction {
 	}
 
 	public void onCall(LuaFunction f) {
-		LuaThread t = globals.running;
-		if (t.inhook) return;
+		if (globals.running.inhook) return;
 		callstack().onCall(f);
-		if (t.hookcall && t.hookfunc != null) 
-			callHook(CALL, NIL);
+		callHook(globals.running.hookfunc, CALL, NIL);
 	}
 
 	public void onCall(LuaClosure c, Varargs varargs, LuaValue[] stack) {
-		LuaThread t = globals.running;
-		if (t.inhook) return;
+		if (globals.running.inhook) return;
 		callstack().onCall(c, varargs, stack);
-		if (t.hookcall && t.hookfunc != null) 
-			callHook(CALL, NIL);
+		callHook(globals.running.hookfunc, CALL, NIL);
 	}
 
 	public void onInstruction(int pc, Varargs v, int top) {
-		LuaThread t = globals.running;
-		if (t.inhook) return;
+		if (globals.running.inhook) return;
 		callstack().onInstruction(pc, v, top);
-		if (t.hookfunc == null) return;
-		if (t.hookcount > 0)
-			if (++t.bytecodes % t.hookcount == 0)
-				callHook(COUNT, NIL);
-		if (t.hookline) {
+		if (globals.running.hookfunc == null) return;
+		if (globals.running.hookcount > 0)
+			if (++globals.running.bytecodes % globals.running.hookcount == 0)
+				callHook(globals.running.hookfunc, COUNT, NIL);
+		if (globals.running.hookline) {
 			int newline = callstack().currentline();
-			if ( newline != t.lastline ) {
-				t.lastline = newline;
-				callHook(LINE, LuaValue.valueOf(newline));
+			if ( newline != globals.running.lastline ) {
+				globals.running.lastline = newline;
+				callHook(globals.running.hookfunc, LINE, LuaValue.valueOf(newline));
 			}
 		}
 	}
 
 	public void onReturn() {
-		LuaThread t = globals.running;
-		if (t.inhook) return;
+		if (globals.running.inhook) return;
 		callstack().onReturn();
-		if (t.hookcall && t.hookfunc != null)
-			callHook(RETURN, NIL);
+		callHook(globals.running.hookfunc, RETURN, NIL);
 	}
 
 	public String traceback(int level) {
 		return callstack().traceback(level);
 	}
 	
-	void callHook(LuaValue type, LuaValue arg) {
-		LuaThread t = globals.running;
-		t.inhook = true;
+	void callHook(LuaValue hookfunc, LuaValue type, LuaValue arg) {
+		if (hookfunc == null) return;
+		LuaThread.State state = globals.running.state;
+		state.set_inhook(true);
 		try {
-			t.hookfunc.call(type, arg);
+			hookfunc.call(type, arg);
 		} catch (LuaError e) {
 			throw e;
 		} catch (RuntimeException e) {
 			throw new LuaError(e);
 		} finally {
-			t.inhook = false;
+			state.set_inhook(false);
 		}
 	}