diff --git a/src/core/org/luaj/vm2/lib/LibFunction.java b/src/core/org/luaj/vm2/lib/LibFunction.java
index 4efcebc8..aeb5050c 100644
--- a/src/core/org/luaj/vm2/lib/LibFunction.java
+++ b/src/core/org/luaj/vm2/lib/LibFunction.java
@@ -282,4 +282,16 @@ abstract public class LibFunction extends LuaFunction {
 			return delegate.oncallv(opcode,varargs);
 		}
 	} 	
+	
+	// -------- code generation helper functions --------
+	
+	// allocate storage for upvalue, leave it empty
+	protected static LuaValue[] newupe() {
+		return new LuaValue[1];
+	}
+
+	// allocate storage for upvalue, initialize with nil
+	protected static LuaValue[] newupn() {
+		return new LuaValue[] { valueOf(777) };
+	}
 } 
diff --git a/src/jse/org/luaj/vm2/luajc/JavaBuilder.java b/src/jse/org/luaj/vm2/luajc/JavaBuilder.java
index 3a96a854..e72e953f 100644
--- a/src/jse/org/luaj/vm2/luajc/JavaBuilder.java
+++ b/src/jse/org/luaj/vm2/luajc/JavaBuilder.java
@@ -92,6 +92,8 @@ public class JavaBuilder {
 	
 	private static final ArrayType TYPE_LOCALUPVALUE = new ArrayType( TYPE_LUAVALUE, 1 );
 	private static final ArrayType TYPE_CHARARRAY = new ArrayType( Type.CHAR, 1 );
+
+	private static final Type[] ARGS_NONE = new Type[0];
 	
 	private static final Class[] NO_INNER_CLASSES = {};
 
@@ -242,7 +244,7 @@ public class JavaBuilder {
 		// add class initializer 
 		if ( ! init.isEmpty() ) {
 			MethodGen mg = new MethodGen(Constants.ACC_STATIC, Type.VOID,
-					new Type[] {}, new String[] {}, "<clinit>", cg
+					ARGS_NONE, new String[] {}, "<clinit>", cg
 							.getClassName(), init, cg.getConstantPool());
 			init.append(InstructionConstants.RETURN);
 			mg.setMaxStack();
@@ -318,13 +320,12 @@ public class JavaBuilder {
 	}
 
 	public void storeLocal(int pc, int slot) {
-		boolean isupval = slots.isUpvalueAssign(pc, slot);
+		boolean isupval = slots.isUpvalue(pc, slot);
 		int index = findSlotIndex( slot, isupval );
 		if (isupval) {
 			boolean isupcreate = slots.isUpvalueCreate(pc, slot);
 			if ( isupcreate ) {
-				append(new PUSH(cp, 1));
-				append(new ANEWARRAY(cp.addClass(STR_LUAVALUE)));
+				append(factory.createInvoke(classname, "newupe", TYPE_LOCALUPVALUE, ARGS_NONE, Constants.INVOKESTATIC));
 				append(InstructionConstants.DUP);
 				append(new ASTORE(index));
 			} else {
@@ -345,12 +346,7 @@ public class JavaBuilder {
 			boolean isupcreate = slots.isUpvalueCreate(pc, slot);
 			if ( isupcreate ) {
 				int index = findSlotIndex( slot, true );
-				append(new PUSH(cp, 1));
-				append(new ANEWARRAY(cp.addClass(STR_LUAVALUE)));
-				dup();
-				append(new PUSH(cp, 0));
-				loadNil();
-				append(InstructionConstants.AASTORE);
+				append(factory.createInvoke(classname, "newupn", TYPE_LOCALUPVALUE, ARGS_NONE, Constants.INVOKESTATIC));
 				append(new ASTORE(index));
 			}
 		}
@@ -397,7 +393,7 @@ public class JavaBuilder {
 
 	public void arg(int argindex) {
 		if ( argindex == 1 ) {
-			append(factory.createInvoke(STR_VARARGS, "arg1", TYPE_LUAVALUE, new Type[] {}, Constants.INVOKEVIRTUAL));
+			append(factory.createInvoke(STR_VARARGS, "arg1", TYPE_LUAVALUE, ARGS_NONE, Constants.INVOKEVIRTUAL));
 		} else {
 			append(new PUSH(cp, argindex));
 			append(factory.createInvoke(STR_VARARGS, "arg", TYPE_LUAVALUE, new Type[] { Type.INT }, Constants.INVOKEVIRTUAL));
@@ -525,7 +521,7 @@ public class JavaBuilder {
 	
 	public void call(int nargs) {
 		switch ( nargs ) {
-		case 0: append(factory.createInvoke(STR_LUAVALUE, "call", TYPE_LUAVALUE, new Type[] {}, Constants.INVOKEVIRTUAL)); break;
+		case 0: append(factory.createInvoke(STR_LUAVALUE, "call", TYPE_LUAVALUE, ARGS_NONE, Constants.INVOKEVIRTUAL)); break;
 		case 1: append(factory.createInvoke(STR_LUAVALUE, "call", TYPE_LUAVALUE, new Type[] { TYPE_LUAVALUE }, Constants.INVOKEVIRTUAL)); break;
 		case 2: append(factory.createInvoke(STR_LUAVALUE, "call", TYPE_LUAVALUE, new Type[] { TYPE_LUAVALUE, TYPE_LUAVALUE }, Constants.INVOKEVIRTUAL)); break;
 		case 3: append(factory.createInvoke(STR_LUAVALUE, "call", TYPE_LUAVALUE, new Type[] { TYPE_LUAVALUE, TYPE_LUAVALUE, TYPE_LUAVALUE }, Constants.INVOKEVIRTUAL)); break;
@@ -540,7 +536,7 @@ public class JavaBuilder {
 	public void invoke(int nargs) {
 		switch ( nargs ) {
 		case -1: append(factory.createInvoke(STR_LUAVALUE, "invoke", TYPE_VARARGS, new Type[] { TYPE_VARARGS }, Constants.INVOKEVIRTUAL)); break;
-		case 0: append(factory.createInvoke(STR_LUAVALUE, "invoke", TYPE_VARARGS, new Type[] {}, Constants.INVOKEVIRTUAL)); break;
+		case 0: append(factory.createInvoke(STR_LUAVALUE, "invoke", TYPE_VARARGS, ARGS_NONE, Constants.INVOKEVIRTUAL)); break;
 		case 1: append(factory.createInvoke(STR_LUAVALUE, "invoke", TYPE_VARARGS, new Type[] { TYPE_VARARGS }, Constants.INVOKEVIRTUAL)); break;
 		case 2: append(factory.createInvoke(STR_LUAVALUE, "invoke", TYPE_VARARGS, new Type[] { TYPE_LUAVALUE, TYPE_VARARGS }, Constants.INVOKEVIRTUAL)); break;
 		case 3: append(factory.createInvoke(STR_LUAVALUE, "invoke", TYPE_VARARGS, new Type[] { TYPE_LUAVALUE, TYPE_LUAVALUE, TYPE_VARARGS }, Constants.INVOKEVIRTUAL)); break;
diff --git a/src/jse/org/luaj/vm2/luajc/JavaGen.java b/src/jse/org/luaj/vm2/luajc/JavaGen.java
index 5de0d8d6..586fd12e 100644
--- a/src/jse/org/luaj/vm2/luajc/JavaGen.java
+++ b/src/jse/org/luaj/vm2/luajc/JavaGen.java
@@ -180,7 +180,7 @@ public class JavaGen {
 				ins = p.code[pc1];
 				if ( Lua.GET_OPCODE(ins) == Lua.OP_TFORLOOP )
 					builder.createUpvalues(pc, Lua.GETARG_A(ins)+3, Lua.GETARG_C(ins));
-				builder.addBranch(pc, JavaBuilder.BRANCH_GOTO, pc+1+sbx);
+				builder.addBranch(pc, JavaBuilder.BRANCH_GOTO, pc1);
 				break;
 			}
 				
@@ -329,14 +329,13 @@ public class JavaGen {
 				builder.loadLocal(pc, a);
 				builder.loadLocal(pc, a+1);
 				builder.loadLocal(pc, a+2);
-				builder.invoke(2);
+				builder.invoke(2); // varresult on stack
 				for ( int i=0; i<c; i++ ) {
 					if ( i+1 < c )
 						builder.dup();
 					builder.arg( i+1 );
 					builder.storeLocal(pc, a+3+i);
 				}
-				
 				builder.loadLocal(pc, a+3);
 				builder.isNil();
 				builder.addBranch(pc, JavaBuilder.BRANCH_IFNE, pc+2);
@@ -376,7 +375,7 @@ public class JavaGen {
 					for ( int up=0; up<nup; ++up ) {
 						if ( up+1 < nup )
 							builder.dup();
-						ins = p.code[++pc];
+						ins = p.code[pc+up+1];
 						b = Lua.GETARG_B(ins);
 						if ( (ins&4) != 0 ) {
 							builder.closureInitUpvalueFromUpvalue( protoname, up, b );
diff --git a/src/jse/org/luaj/vm2/luajc/Slots.java b/src/jse/org/luaj/vm2/luajc/Slots.java
index 8eedfedc..6ee41e13 100644
--- a/src/jse/org/luaj/vm2/luajc/Slots.java
+++ b/src/jse/org/luaj/vm2/luajc/Slots.java
@@ -59,8 +59,9 @@ public class Slots {
 		return false;
 	}
 	
-	public boolean isUpvalueAssign(int pc, int slot) {
+	public boolean isUpvalue(int pc, int slot) {
 		switch (slots[pc+1][slot]) {
+		case UPVAL_USE:
 		case UPVAL_CREATE:
 		case UPVAL_USE_CREATE:
 		case UPVAL_USE_ASSIGN:
@@ -342,7 +343,7 @@ public class Slots {
 					int sbx = Lua.GETARG_sBx(i);
 					if ( o == Lua.OP_JMP && (pc0 + 1 + sbx == pc1) ) {
 						for ( int j=0; j<c; j++ ) {
-							checkPromoteLoopUpvalue( pc0, pc1, a+3+j );
+							checkPromoteLoopUpvalue( pc0+1, pc1+1, a+3+j );
 						}
 					}
 				}
@@ -351,16 +352,16 @@ public class Slots {
 		
 	}
 	
-	private void checkPromoteLoopUpvalue(int pc0, int pc1, int slot) {
-		for ( int index=pc0+1; index<=pc1; ++index ) {
+	private void checkPromoteLoopUpvalue(int index0, int index1, int slot) {
+		for ( int index=index0; index<=index1; ++index ) {
 			switch (slots[index][slot]) {
 			case UPVAL_CREATE:
 			case UPVAL_USE_CREATE:
 			case UPVAL_USE_ASSIGN:
 			case UPVAL_USE:
-				int i = pc0;
-				slots[++i][slot] = UPVAL_CREATE;
-				while ( ++i<=pc1 )
+				int i = index0;
+				slots[i][slot] = UPVAL_CREATE;
+				while ( ++i<=index1 )
 					slots[i][slot] = UPVAL_USE;
 				return;
 			}