diff --git a/src/core/org/luaj/lib/BaseLib.java b/src/core/org/luaj/lib/BaseLib.java
index dfa03d55..a52357c7 100644
--- a/src/core/org/luaj/lib/BaseLib.java
+++ b/src/core/org/luaj/lib/BaseLib.java
@@ -118,7 +118,8 @@ public class BaseLib extends LFunction {
 						Lua.TYPE_NAMES[type]+" expected, got no value)") );
 	}
 
-	private void checkargtype(LuaState vm, int index, int type) {		
+	private void checkargtype
+	(LuaState vm, int index, int type) {		
 		checkargexists( vm, index, type );
 		int t = vm.type(index);
 		if ( t != type ) {
@@ -164,8 +165,11 @@ public class BaseLib extends LFunction {
 		}
 		case SETMETATABLE: {
 			checkargtype(vm,2,Lua.LUA_TTABLE);
+			if ( vm.gettop()<3 || ! (vm.isnil(3) || vm.istable(3)) )
+				vm.error( "bad argument #2 to '?' (nil or table expected)" );
 			vm.setmetatable(2);
 			vm.remove(1);
+			vm.settop(1);
 			break;
 		}		
 		case TYPE: {
diff --git a/src/core/org/luaj/lib/PackageLib.java b/src/core/org/luaj/lib/PackageLib.java
index 81ec0e63..af907669 100644
--- a/src/core/org/luaj/lib/PackageLib.java
+++ b/src/core/org/luaj/lib/PackageLib.java
@@ -43,7 +43,7 @@ public class PackageLib extends LFunction {
 	
 	public static InputStream STDIN = null;
 	public static PrintStream STDOUT = System.out;
-	public static LTable      LOADED = new LTable();
+	public static LTable      LOADED = null;
 
 	private static final LString _M = new LString("_M");
 	private static final LString _NAME = new LString("_NAME");	
@@ -86,6 +86,7 @@ public class PackageLib extends LFunction {
 		pckg = new LTable();
 		for ( int i=LOADLIB; i<=SEEALL; i++ )
 			pckg.put( NAMES[i], new PackageLib(i) );
+		LOADED = new LTable();
 		pckg.put( "loaded", LOADED );
 		pckg.put( _PRELOAD, new LTable() );
 		LTable loaders = new LTable(3,0);
diff --git a/src/core/org/luaj/vm/LTable.java b/src/core/org/luaj/vm/LTable.java
index 6116390e..e9066d78 100644
--- a/src/core/org/luaj/vm/LTable.java
+++ b/src/core/org/luaj/vm/LTable.java
@@ -85,8 +85,6 @@ public class LTable extends LValue {
 	
 	private LTable m_metatable;
 	
-	
-	
 	/** Construct an empty LTable with no initial capacity. */
 	public LTable() {
 		m_vector = EMPTY_ARRAY;
@@ -273,8 +271,14 @@ public class LTable extends LValue {
 
 	/** Valid for tables */
 	public void luaSetMetatable(LValue metatable) {
-		this.m_metatable = ( metatable != null && metatable != LNil.NIL ) ?
-					(LTable) metatable : null;
+		if ( m_metatable != null &&  m_metatable.containsKey(TM_METATABLE) )
+			throw new LuaErrorException("cannot change a protected metatable");
+		if ( metatable == null || metatable == LNil.NIL )
+			this.m_metatable = null;
+		else if ( metatable.luaGetType() == Lua.LUA_TTABLE ) 
+			this.m_metatable = (LTable) metatable;
+		else
+			throw new LuaErrorException("nil or table expected, got "+metatable.luaGetTypeName());
 	}
 
 	public String toJavaString() {
diff --git a/src/core/org/luaj/vm/LValue.java b/src/core/org/luaj/vm/LValue.java
index bb1fa380..dce05f83 100644
--- a/src/core/org/luaj/vm/LValue.java
+++ b/src/core/org/luaj/vm/LValue.java
@@ -31,6 +31,9 @@ public class LValue {
 	/** Metatable tag for intercepting table sets */
 	public static final LString TM_NEWINDEX = new LString("__newindex");
 	
+	/** Metatable tag for intercepting table sets */
+	public static final LString TM_METATABLE = new LString("__metatable");
+	
 	protected void conversionError(String target) {
 		throw new LuaErrorException( "bad conversion: "+luaGetTypeName()+" to "+target );
 	}
@@ -70,12 +73,12 @@ public class LValue {
 
 	// unsupported except for numbers
 	public LValue luaBinOpInteger(int opcode, int m_value) {
-		return arithmeticError("number");
+		return arithmeticError(luaGetTypeName());
 	}
 
 	// unsupported except for numbers
 	public LValue luaBinOpDouble(int opcode, double m_value) {
-		return arithmeticError("number");
+		return arithmeticError(luaGetTypeName());
 	}
 
 	// unsupported except for numbers, strings, and == with various combinations of Nil, Boolean, etc. 
diff --git a/src/test/java/org/luaj/vm/LuaJTest.java b/src/test/java/org/luaj/vm/LuaJTest.java
index feae903b..4e4ef7d3 100644
--- a/src/test/java/org/luaj/vm/LuaJTest.java
+++ b/src/test/java/org/luaj/vm/LuaJTest.java
@@ -141,7 +141,7 @@ public class LuaJTest extends TestCase {
 	private void runTest( String testName ) throws IOException, InterruptedException {
 
 		// new lua state 
-		LuaState state = new DebugLuaState();
+		LuaState state = LuaState.newState();
 		
         // add standard bindings
 		state.installStandardLibs();
diff --git a/src/test/res/baselib.lua b/src/test/res/baselib.lua
index 155eecce..9b704db7 100644
--- a/src/test/res/baselib.lua
+++ b/src/test/res/baselib.lua
@@ -1,14 +1,6 @@
 -- unit tests for functions in BaseLib.java
-local ids = {}
-local function id(obj)
-	local v = ids[obj]
-	if v then
-		return v
-	end
-	table.insert(ids,obj)
-	ids[obj] = type(obj)..'.'..tostring(#ids)
-	return ids[obj]
-end 
+package.path = "?.lua;src/test/res/?.lua"
+require 'ids'
 
 -- print
 print()
diff --git a/src/test/res/errors.lua b/src/test/res/errors.lua
index 8fe2af99..a6410661 100644
--- a/src/test/res/errors.lua
+++ b/src/test/res/errors.lua
@@ -1,7 +1,6 @@
 -- object ids
 package.path = "?.lua;src/test/res/?.lua"
 require 'ids'
-ids = {}
 
 -- test of common types of errors
 local function c(f,...) return f(...) end
@@ -9,7 +8,6 @@ local function b(...) return c(...) end
 local function a(...) return pcall(b,...) end
 s = 'some string'
 local t = {}
-
 -- error message tests
 print( 'a(error)', a(error) )
 print( 'a(error,"msg")', a(error,"msg") )
diff --git a/src/test/res/metatables.lua b/src/test/res/metatables.lua
index 1b7faea3..9593b40c 100644
--- a/src/test/res/metatables.lua
+++ b/src/test/res/metatables.lua
@@ -1,5 +1,31 @@
+package.path = "?.lua;src/test/res/?.lua"
+require 'ids'
+
 -- The purpose of this test case is to demonstrate that
 -- basic metatable operations on non-table types work.
 -- i.e. that s.sub(s,...) could be used in place of string.sub(s,...)
 local s = "hello"
 print(s:sub(2,4))
+
+local t = {}
+function op(name,...)
+	a,b,c,d = pcall( setmetatable, t, ... )
+	print( name, id(t), id(getmetatable(t)), id(a), id(b), id(c), id(d) )
+end
+op('set{}  ',{})
+op('set-nil',nil)
+op('set{}  ',{})
+op('set')
+op('set{}  ',{})
+op('set{}  ',{})
+op('set{}{}',{},{})
+op('set-nil',nil)
+op('set{__}',{__metatable={}})
+op('set{}  ',{})
+op('set-nil',nil)
+t = {}
+op('set{}  ',{})
+op('set-nil',nil)
+op('set{__}',{__metatable='abc'})
+op('set{}  ',{})
+op('set-nil',nil)
diff --git a/src/test/res/require.lua b/src/test/res/require.lua
index 00faa91f..73e376b6 100644
--- a/src/test/res/require.lua
+++ b/src/test/res/require.lua
@@ -1,18 +1,6 @@
 -- unit tests for require() function
-local ids = {}
-local ti = table.insert
-local function id(obj)
-	if not obj or type(obj) == 'number' or type(obj) == 'string' or type(obj) == 'boolean' then
-		return obj
-	end
-	local v = ids[obj]
-	if v then
-		return v
-	end
-	ti(ids,obj)
-	ids[obj] = type(obj)..'.'..tostring(#ids)
-	return ids[obj]
-end 
+package.path = "?.lua;src/test/res/?.lua"
+require 'ids'
 
 -- tests on require
 package.path='?.lua;src/test/res/?.lua'