diff --git a/src/core/org/luaj/vm2/LuaThread.java b/src/core/org/luaj/vm2/LuaThread.java
index 1acfcfcf..05d1477d 100644
--- a/src/core/org/luaj/vm2/LuaThread.java
+++ b/src/core/org/luaj/vm2/LuaThread.java
@@ -138,7 +138,7 @@ public class LuaThread extends LuaValue implements Runnable {
 	}
 
 	public static final LuaFunction getCallstackFunction(int level) {
-		return level>0 || level<running_thread.calls? 
+		return level>=0 && level<running_thread.calls? 
 			running_thread.callstack[running_thread.calls-level-1]:
 			null;
 	}
diff --git a/src/core/org/luaj/vm2/lib/PackageLib.java b/src/core/org/luaj/vm2/lib/PackageLib.java
index 21d62c44..81205508 100644
--- a/src/core/org/luaj/vm2/lib/PackageLib.java
+++ b/src/core/org/luaj/vm2/lib/PackageLib.java
@@ -351,17 +351,18 @@ public class PackageLib extends LuaTable {
 	
 	private LuaValue loader_Java( Varargs args ) {
 		String name = args.checkString(1);
+		String classname = toClassname( name );
 		Class c = null;
 		LuaValue v = null;
 		try {
-			c = Class.forName(name.replace('/', '.'));
+			c = Class.forName(classname);
 			v = (LuaValue) c.newInstance();
 			v.setfenv(_G);
 			return v;
 		} catch ( ClassNotFoundException  cnfe ) {
-			return valueOf("\n\tno class '"+name+"'" );
+			return valueOf("\n\tno class '"+classname+"'" );
 		} catch ( Exception e ) {
-			return valueOf("\n\tjava load failed on '"+name+"', "+e );
+			return valueOf("\n\tjava load failed on '"+classname+"', "+e );
 		}
 	}
 	
@@ -373,10 +374,10 @@ public class PackageLib extends LuaTable {
 			j -= 4;
 		for ( int k=0; k<j; k++ ) {
 			char c = filename.charAt(k);
-			if ( (!isClassnamePart(c)) && (c!='/') && (c!='\\') ) {
+			if ( (!isClassnamePart(c)) || (c=='/') || (c=='\\') ) {
 				StringBuffer sb = new StringBuffer(j);
 				for ( int i=0; i<j; i++ ) {
-					c = filename.charAt(k);
+					c = filename.charAt(i);
 					sb.append( 
 							 (isClassnamePart(c))? c:
 							 ((c=='/') || (c=='\\'))? '.': '_' ); 
diff --git a/src/core/org/luaj/vm2/lib/VarArgFunction.java b/src/core/org/luaj/vm2/lib/VarArgFunction.java
index 48ec6762..7a96b8a3 100644
--- a/src/core/org/luaj/vm2/lib/VarArgFunction.java
+++ b/src/core/org/luaj/vm2/lib/VarArgFunction.java
@@ -21,13 +21,11 @@
 ******************************************************************************/
 package org.luaj.vm2.lib;
 
+import org.luaj.vm2.LuaThread;
 import org.luaj.vm2.LuaValue;
 import org.luaj.vm2.Varargs;
 
 abstract public class VarArgFunction extends LibFunction {
-
-	abstract public Varargs invoke(Varargs args);
-	
 	public VarArgFunction() {
 	}
 	
@@ -54,4 +52,18 @@ abstract public class VarArgFunction extends LibFunction {
 	public LuaValue call(LuaValue arg1, LuaValue arg2, LuaValue arg3) {
 		return invoke(varargsOf(arg1,arg2,arg3)).arg1();
 	}
+
+	public Varargs invoke(Varargs args) {
+		LuaThread.onCall(this);
+		try {
+			return onInvoke(args);
+		} finally {
+			LuaThread.onReturn();
+		}
+	}
+
+	protected Varargs onInvoke(Varargs args) {
+		return NONE;
+	}
+	
 } 
diff --git a/src/jse/org/luaj/vm2/luajc/JavaBytecodeGenerator.java b/src/jse/org/luaj/vm2/luajc/JavaBytecodeGenerator.java
index dae37af7..ad974404 100644
--- a/src/jse/org/luaj/vm2/luajc/JavaBytecodeGenerator.java
+++ b/src/jse/org/luaj/vm2/luajc/JavaBytecodeGenerator.java
@@ -254,7 +254,7 @@ public class JavaBytecodeGenerator {
 			nl = p.maxstacksize;
 			locals = new LocalVariableGen[nl];
 			
-			// implement LuaValue.invoke(Varargs args)
+			// implement LuaValue.onInvoke(Varargs args)
 			init = new InstructionList();
 			il = new InstructionList();
 			mg = new MethodGen(
@@ -262,7 +262,7 @@ public class JavaBytecodeGenerator {
 					TYPE_VARARGS, // return type
 					new Type[] { TYPE_VARARGS }, // argument types
 					new String[] { "args" }, // arg names
-					"invoke", STR_LUAVALUE, // method, class
+					"onInvoke", STR_LUAVALUE, // method, class
 					il, cp);
 			factory = new InstructionFactory(cg);