diff --git a/vm/vm.go b/vm/vm.go
index 968ca10fa..22172cb3a 100644
--- a/vm/vm.go
+++ b/vm/vm.go
@@ -21,7 +21,7 @@ func New(env Environment, typ Type) VirtualMachine {
 }
 
 func (self *Vm) Run(me, caller ClosureRef, code []byte, value, gas, price *big.Int, data []byte) (ret []byte, err error) {
-	return nil, nil
+	panic("not implemented")
 }
 
 func (self *Vm) Env() Environment {