diff --git a/src/core/org/luaj/vm2/LuaTable.java b/src/core/org/luaj/vm2/LuaTable.java
index df706230..8201333c 100644
--- a/src/core/org/luaj/vm2/LuaTable.java
+++ b/src/core/org/luaj/vm2/LuaTable.java
@@ -119,9 +119,34 @@ public class LuaTable extends LuaValue {
 		if ( m_metatable!=null && !m_metatable.rawget(METATABLE).isnil() )
 			error("cannot change a protected metatable");
 		m_metatable = metatable;
+		LuaValue mode;
+		if ( m_metatable!=null && (mode=m_metatable.rawget(MODE)).isstring() ) {
+			String m = mode.toString();
+			return changemode(m.contains("k"),m.contains("v"));
+		}
 		return this;
 	}
 	
+	protected LuaTable changemode(boolean weakkeys, boolean weakvalues) {
+		if ( weakkeys || weakvalues ) {
+			return recreateas(weakkeys, weakvalues);
+		}
+		return this;
+	}
+
+	protected LuaTable recreateas(boolean weakkeys, boolean weakvalues) {
+		LuaTable t = weakkeys||weakvalues? 
+				new WeakTable(weakkeys, weakvalues): 
+				new LuaTable();
+		t.presize(array.length,hashKeys.length);
+		Varargs n;
+		LuaValue k = NIL;
+		while ( !(k = ((n = next(k)).arg1())).isnil() )
+			t.rawset(k, n.arg(2));
+		t.m_metatable = m_metatable;
+		return t;
+	}
+
 	public LuaValue get( int key ) {
 		LuaValue v = rawget(key);
 		return v.isnil() && m_metatable!=null? gettable(this,valueOf(key)): v;
diff --git a/src/core/org/luaj/vm2/LuaValue.java b/src/core/org/luaj/vm2/LuaValue.java
index 022ceb3d..b46d238e 100644
--- a/src/core/org/luaj/vm2/LuaValue.java
+++ b/src/core/org/luaj/vm2/LuaValue.java
@@ -298,8 +298,7 @@ public class LuaValue extends Varargs {
 	
 	// lua number/string conversion
 	public LuaString strvalue()     { typerror("strValue"); return null; }
-	public LuaValue    strongvalue()  { return this; }
-	
+	public LuaValue  strongvalue()  { return this; }
 
 	// conversion from java values
 	public static LuaBoolean  valueOf(boolean b)    { return b? LuaValue.TRUE: FALSE; };
diff --git a/src/core/org/luaj/vm2/WeakTable.java b/src/core/org/luaj/vm2/WeakTable.java
index 3b320650..4514c5b1 100644
--- a/src/core/org/luaj/vm2/WeakTable.java
+++ b/src/core/org/luaj/vm2/WeakTable.java
@@ -38,36 +38,41 @@ public class WeakTable extends LuaTable {
 			ref = new WeakReference(val);
 		}
 		public int type() {
-			return LuaValue.TNIL;
+			return strongvalue().type();
 		}
 		public String typename() {
-			return "value";
+			return "weakvalue";
 		}
 		public LuaValue strongvalue() {
 			Object o = ref.get();
 			return o!=null? (LuaValue)o: NIL;
 		}
+		public String toString() {
+			return strongvalue().toString();
+		}
 	}
 	
 	private static class WeakUserdata extends LuaValue {
-		private final WeakReference ref;
-		private LuaValue metatable;
+		private WeakReference ref;
+		private WeakReference mt;
 		public WeakUserdata(Object val, LuaValue metatable) {
-			ref = new WeakReference(val);
+			this.ref = new WeakReference(val);
+			this.mt = new WeakReference(metatable);
 		}
 		public int type() {
-			return LuaValue.TNIL;
+			return TVALUE;
 		}
 		public String typename() {
-			return "value";
+			return "weakuserdata";
 		}
 		public LuaValue strongvalue() {
-			Object o = ref.get();
-			if ( o == null ) {
-				metatable = null;
-				return NIL;
+			if ( ref != null ) {
+				Object o = ref.get();
+				if ( o != null )
+					return userdataOf( o, (LuaValue) mt.get() );
 			}
-			return userdataOf( o, metatable );
+			ref = mt = null;
+			return NIL;
 		}
 	}
 	
@@ -135,7 +140,7 @@ public class WeakTable extends LuaTable {
 		v = v.strongvalue();
 		if ( v.isnil() ) {
 			// TODO: mark table for culling? 
-			rawset(key, NIL);
+			super.rawset(key, NIL);
 		}
 		return v;
 	}
@@ -147,7 +152,7 @@ public class WeakTable extends LuaTable {
 		v = v.strongvalue();
 		if ( v.isnil() ) {
 			// TODO: mark table for culling? 
-			rawset(key, NIL);
+			super.rawset(key, NIL);
 		}
 		return v;
 	}
@@ -176,4 +181,12 @@ public class WeakTable extends LuaTable {
 			}
 		}
 	}
+	
+	protected LuaTable changemode(boolean k, boolean v) {
+		if ( k!=this.weakKeys || v!=weakValues )
+			return recreateas(k,v);
+		return this;
+	}
+
+
 }
diff --git a/src/core/org/luaj/vm2/lib/BaseLib.java b/src/core/org/luaj/vm2/lib/BaseLib.java
index 081edffa..3982ddcb 100644
--- a/src/core/org/luaj/vm2/lib/BaseLib.java
+++ b/src/core/org/luaj/vm2/lib/BaseLib.java
@@ -317,8 +317,7 @@ public class BaseLib extends OneArgFunction implements ResourceFinder {
 		case 13: { // "setmetatable", // (table, metatable) -> table
 			final LuaValue t = args.arg1();
 			final LuaValue mt = args.checkvalue(2);
-			t.setmetatable(mt.isnil()? null: mt.checktable());
-			return t;
+			return t.setmetatable(mt.isnil()? null: mt.checktable());
 		}
 		case 14: { // "tostring", // (e) -> value
 			LuaValue arg = args.checkvalue(1);