diff --git a/ethereal/ui/ui_lib.go b/ethereal/ui/ui_lib.go
index adba177d0..fde2697b8 100644
--- a/ethereal/ui/ui_lib.go
+++ b/ethereal/ui/ui_lib.go
@@ -94,7 +94,40 @@ type memAddr struct {
 	Value string
 }
 
-func (ui *UiLib) DebugTx(recipient, valueStr, gasStr, gasPriceStr, data string) (string, error) {
+type Debugger struct {
+	ui   *UiLib
+	next chan bool
+}
+
+func (d *Debugger) halting(op ethchain.OpCode, mem *ethchain.Memory, stack *ethchain.Stack) {
+	d.ui.win.Root().Call("clearMem")
+	d.ui.win.Root().Call("clearStack")
+
+	addr := 0
+	for i := 0; i+32 <= mem.Len(); i += 32 {
+		d.ui.win.Root().Call("setMem", memAddr{fmt.Sprintf("%03d", addr), fmt.Sprintf("% x", mem.Data()[i:i+32])})
+		addr++
+	}
+
+	for _, val := range stack.Data() {
+		d.ui.win.Root().Call("setStack", val.String())
+	}
+
+out:
+	for {
+		select {
+		case <-d.next:
+			break out
+		default:
+		}
+	}
+}
+
+func (d *Debugger) Next() {
+	d.next <- true
+}
+
+func (ui *UiLib) DebugTx(recipient, valueStr, gasStr, gasPriceStr, data string) {
 	state := ui.eth.BlockChain().CurrentBlock.State()
 
 	asm, err := mutan.Compile(strings.NewReader(data), false)
@@ -126,21 +159,12 @@ func (ui *UiLib) DebugTx(recipient, valueStr, gasStr, gasPriceStr, data string)
 		Diff:        block.Difficulty,
 		TxData:      nil,
 	})
-	callerClosure.Call(vm, nil, func(op ethchain.OpCode, mem *ethchain.Memory, stack *ethchain.Stack) {
-		ui.win.Root().Call("clearMem")
-		ui.win.Root().Call("clearStack")
 
-		addr := 0
-		for i := 0; i+32 <= mem.Len(); i += 32 {
-			ui.win.Root().Call("setMem", memAddr{fmt.Sprintf("%03d", addr), fmt.Sprintf("% x", mem.Data()[i:i+32])})
-			addr++
-		}
+	db := &Debugger{ui, make(chan bool)}
+	ui.engine.Context().SetVar("db", db)
+	go func() {
+		callerClosure.Call(vm, nil, db.halting)
 
-		for _, val := range stack.Data() {
-			ui.win.Root().Call("setStack", val.String())
-		}
-	})
-	state.Reset()
-
-	return "", nil
+		state.Reset()
+	}()
 }