diff --git a/golang/cosmos/app/app.go b/golang/cosmos/app/app.go
index b80fff91c53..51205c13dee 100644
--- a/golang/cosmos/app/app.go
+++ b/golang/cosmos/app/app.go
@@ -358,7 +358,12 @@ func NewAgoricApp(
 	)
 
 	// This function is tricky to get right, so we build it ourselves.
-	callToController := func(ctx sdk.Context, str string) (string, error) {
+	callToController := func(ctx sdk.Context, str, simReturn string) (string, error) {
+		if vm.IsSimulation(ctx) {
+			// Just return the simReturn, since the message is being simulated.
+			return simReturn, nil
+		}
+		// We use SwingSet-level metering to charge the user for the call.
 		app.MustInitController(ctx)
 		defer vm.SetControllerContext(ctx)()
 		return sendToController(true, str)
@@ -565,7 +570,7 @@ func (app *GaiaApp) MustInitController(ctx sdk.Context) {
 	}
 	bz, err := json.Marshal(action)
 	if err == nil {
-		_, err = app.SwingSetKeeper.CallToController(ctx, string(bz))
+		_, err = app.SwingSetKeeper.CallToController(ctx, string(bz), "")
 	}
 	if err != nil {
 		fmt.Fprintln(os.Stderr, "Cannot initialize Controller", err)
diff --git a/golang/cosmos/vm/controller.go b/golang/cosmos/vm/controller.go
index f73a3765c7f..ece940a7060 100644
--- a/golang/cosmos/vm/controller.go
+++ b/golang/cosmos/vm/controller.go
@@ -25,6 +25,8 @@ var nameToPort = make(map[string]int)
 var lastPort = 0
 
 func SetControllerContext(ctx sdk.Context) func() {
+	// We are only called by the controller, so we assume that it is billing its
+	// own meter usage.
 	controllerContext.Context = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
 	return func() {
 		controllerContext.Context = sdk.Context{}
diff --git a/golang/cosmos/x/swingset/abci.go b/golang/cosmos/x/swingset/abci.go
index 3802b2d1c04..f4310e3f563 100644
--- a/golang/cosmos/x/swingset/abci.go
+++ b/golang/cosmos/x/swingset/abci.go
@@ -49,7 +49,7 @@ func BeginBlock(ctx sdk.Context, req abci.RequestBeginBlock, keeper Keeper) erro
 		return sdkerrors.Wrap(sdkerrors.ErrJSONMarshal, err.Error())
 	}
 
-	_, err = keeper.CallToController(ctx, string(b))
+	_, err = keeper.CallToController(ctx, string(b), "")
 
 	// fmt.Fprintln(os.Stderr, "Returned from SwingSet", out, err)
 	return err
@@ -71,7 +71,7 @@ func EndBlock(ctx sdk.Context, req abci.RequestEndBlock, keeper Keeper) ([]abci.
 		return nil, sdkerrors.Wrap(sdkerrors.ErrJSONMarshal, err.Error())
 	}
 
-	_, err = keeper.CallToController(ctx, string(b))
+	_, err = keeper.CallToController(ctx, string(b), "")
 
 	// fmt.Fprintln(os.Stderr, "Returned from SwingSet", out, err)
 	if err != nil {
@@ -102,7 +102,7 @@ func CommitBlock(keeper Keeper) error {
 		return sdkerrors.Wrap(sdkerrors.ErrJSONMarshal, err.Error())
 	}
 
-	_, err = keeper.CallToController(sdk.Context{}, string(b))
+	_, err = keeper.CallToController(sdk.Context{}, string(b), "")
 
 	// fmt.Fprintln(os.Stderr, "Returned from SwingSet", out, err)
 	if err != nil {
diff --git a/golang/cosmos/x/swingset/genesis.go b/golang/cosmos/x/swingset/genesis.go
index 8aab1e848e2..787df9265e5 100644
--- a/golang/cosmos/x/swingset/genesis.go
+++ b/golang/cosmos/x/swingset/genesis.go
@@ -53,7 +53,7 @@ func InitGenesis(ctx sdk.Context, keeper Keeper, data *types.GenesisState) []abc
 		panic(err)
 	}
 
-	_, err = keeper.CallToController(ctx, string(b))
+	_, err = keeper.CallToController(ctx, string(b), "")
 
 	if err != nil {
 		// NOTE: A failed BOOTSTRAP_BLOCK means that the SwingSet state is inconsistent.
diff --git a/golang/cosmos/x/swingset/handler.go b/golang/cosmos/x/swingset/handler.go
index 8baac4b5731..96a184b901b 100644
--- a/golang/cosmos/x/swingset/handler.go
+++ b/golang/cosmos/x/swingset/handler.go
@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/Agoric/agoric-sdk/golang/cosmos/vm"
 	"github.com/Agoric/agoric-sdk/golang/cosmos/x/swingset/keeper"
 
 	sdk "github.com/cosmos/cosmos-sdk/types"
@@ -17,14 +16,6 @@ func NewHandler(k Keeper) sdk.Handler {
 	msgServer := keeper.NewMsgServerImpl(k)
 
 	return func(ctx sdk.Context, msg sdk.Msg) (*sdk.Result, error) {
-		if vm.IsSimulation(ctx) {
-			// We don't support simulation.
-			return &sdk.Result{}, nil
-		} else {
-			// The simulation was done, so now allow infinite gas.
-			ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-		}
-
 		ctx = ctx.WithEventManager(sdk.NewEventManager())
 
 		switch msg := msg.(type) {
diff --git a/golang/cosmos/x/swingset/keeper/keeper.go b/golang/cosmos/x/swingset/keeper/keeper.go
index c68500ab92b..58cc1fb34f5 100644
--- a/golang/cosmos/x/swingset/keeper/keeper.go
+++ b/golang/cosmos/x/swingset/keeper/keeper.go
@@ -26,7 +26,7 @@ type Keeper struct {
 	bankKeeper    bankkeeper.Keeper
 
 	// CallToController dispatches a message to the controlling process
-	CallToController func(ctx sdk.Context, str string) (string, error)
+	CallToController func(ctx sdk.Context, str, simReturn string) (string, error)
 }
 
 // A prefix of bytes, since KVStores can't handle empty slices as keys.
@@ -48,7 +48,7 @@ func stringToKey(keyStr string) []byte {
 func NewKeeper(
 	cdc codec.Codec, key sdk.StoreKey,
 	accountKeeper authkeeper.AccountKeeper, bankKeeper bankkeeper.Keeper,
-	callToController func(ctx sdk.Context, str string) (string, error),
+	callToController func(ctx sdk.Context, str, simReturn string) (string, error),
 ) Keeper {
 
 	return Keeper{
diff --git a/golang/cosmos/x/swingset/keeper/msg_server.go b/golang/cosmos/x/swingset/keeper/msg_server.go
index c787919234d..8578f7061bc 100644
--- a/golang/cosmos/x/swingset/keeper/msg_server.go
+++ b/golang/cosmos/x/swingset/keeper/msg_server.go
@@ -58,7 +58,7 @@ func (keeper msgServer) DeliverInbound(goCtx context.Context, msg *types.MsgDeli
 		return nil, sdkerrors.Wrap(sdkerrors.ErrJSONMarshal, err.Error())
 	}
 
-	_, err = keeper.CallToController(ctx, string(b))
+	_, err = keeper.CallToController(ctx, string(b), "")
 	// fmt.Fprintln(os.Stderr, "Returned from SwingSet", out, err)
 	if err != nil {
 		return nil, err
@@ -104,7 +104,7 @@ func (keeper msgServer) Provision(goCtx context.Context, msg *types.MsgProvision
 		return nil, err
 	}
 
-	_, err = keeper.CallToController(ctx, string(b))
+	_, err = keeper.CallToController(ctx, string(b), "")
 	// fmt.Fprintln(os.Stderr, "Returned from SwingSet", out, err)
 	if err != nil {
 		return nil, err
diff --git a/golang/cosmos/x/swingset/storage.go b/golang/cosmos/x/swingset/storage.go
index 60630005ff7..6bfa8d831e0 100644
--- a/golang/cosmos/x/swingset/storage.go
+++ b/golang/cosmos/x/swingset/storage.go
@@ -23,7 +23,7 @@ func NewStorageHandler(keeper Keeper) storageHandler {
 	return storageHandler{keeper: keeper}
 }
 
-func (sh storageHandler) Receive(ctx *vm.ControllerContext, str string) (ret string, err error) {
+func (sh storageHandler) Receive(cctx *vm.ControllerContext, str string) (ret string, err error) {
 	keeper := sh.keeper
 	msg := new(storageMessage)
 	err = json.Unmarshal([]byte(str), &msg)
@@ -38,7 +38,7 @@ func (sh storageHandler) Receive(ctx *vm.ControllerContext, str string) (ret str
 			case sdk.ErrorOutOfGas:
 				err = fmt.Errorf(
 					"out of gas in location: %v; gasUsed: %d",
-					rType.Descriptor, ctx.Context.GasMeter().GasConsumed(),
+					rType.Descriptor, cctx.Context.GasMeter().GasConsumed(),
 				)
 			default:
 				// Not ErrorOutOfGas, so panic again.
@@ -53,11 +53,11 @@ func (sh storageHandler) Receive(ctx *vm.ControllerContext, str string) (ret str
 		storage := NewStorage()
 		storage.Value = msg.Value
 		//fmt.Printf("giving Keeper.SetStorage(%s) %s\n", msg.Key, storage.Value)
-		keeper.SetStorage(ctx.Context, msg.Key, storage)
+		keeper.SetStorage(cctx.Context, msg.Key, storage)
 		return "true", nil
 
 	case "get":
-		storage := keeper.GetStorage(ctx.Context, msg.Key)
+		storage := keeper.GetStorage(cctx.Context, msg.Key)
 		if storage.Value == "" {
 			return "null", nil
 		}
@@ -69,14 +69,14 @@ func (sh storageHandler) Receive(ctx *vm.ControllerContext, str string) (ret str
 		return string(s), nil
 
 	case "has":
-		storage := keeper.GetStorage(ctx.Context, msg.Key)
+		storage := keeper.GetStorage(cctx.Context, msg.Key)
 		if storage.Value == "" {
 			return "false", nil
 		}
 		return "true", nil
 
 	case "keys":
-		keys := keeper.GetKeys(ctx.Context, msg.Key)
+		keys := keeper.GetKeys(cctx.Context, msg.Key)
 		if keys.Keys == nil {
 			return "[]", nil
 		}
@@ -87,12 +87,12 @@ func (sh storageHandler) Receive(ctx *vm.ControllerContext, str string) (ret str
 		return string(bytes), nil
 
 	case "entries":
-		keys := keeper.GetKeys(ctx.Context, msg.Key)
+		keys := keeper.GetKeys(cctx.Context, msg.Key)
 		ents := make([][]string, len(keys.Keys))
 		for i, key := range keys.Keys {
 			ents[i] = make([]string, 2)
 			ents[i][0] = key
-			storage := keeper.GetStorage(ctx.Context, fmt.Sprintf("%s.%s", msg.Key, key))
+			storage := keeper.GetStorage(cctx.Context, fmt.Sprintf("%s.%s", msg.Key, key))
 			ents[i][1] = storage.Value
 		}
 		bytes, err := json.Marshal(ents)
@@ -102,10 +102,10 @@ func (sh storageHandler) Receive(ctx *vm.ControllerContext, str string) (ret str
 		return string(bytes), nil
 
 	case "values":
-		keys := keeper.GetKeys(ctx.Context, msg.Key)
+		keys := keeper.GetKeys(cctx.Context, msg.Key)
 		vals := make([]string, len(keys.Keys))
 		for i, key := range keys.Keys {
-			storage := keeper.GetStorage(ctx.Context, fmt.Sprintf("%s.%s", msg.Key, key))
+			storage := keeper.GetStorage(cctx.Context, fmt.Sprintf("%s.%s", msg.Key, key))
 			vals[i] = storage.Value
 		}
 		bytes, err := json.Marshal(vals)
@@ -115,7 +115,7 @@ func (sh storageHandler) Receive(ctx *vm.ControllerContext, str string) (ret str
 		return string(bytes), nil
 
 	case "size":
-		keys := keeper.GetKeys(ctx.Context, msg.Key)
+		keys := keeper.GetKeys(cctx.Context, msg.Key)
 		if keys.Keys == nil {
 			return "0", nil
 		}
diff --git a/golang/cosmos/x/vbank/handler.go b/golang/cosmos/x/vbank/handler.go
index 9613e404b7d..2b8ac529765 100644
--- a/golang/cosmos/x/vbank/handler.go
+++ b/golang/cosmos/x/vbank/handler.go
@@ -3,7 +3,6 @@ package vbank
 import (
 	"fmt"
 
-	"github.com/Agoric/agoric-sdk/golang/cosmos/vm"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 )
@@ -11,14 +10,6 @@ import (
 // NewHandler returns a handler for "vbank" type messages.
 func NewHandler(keeper Keeper) sdk.Handler {
 	return func(ctx sdk.Context, msg sdk.Msg) (*sdk.Result, error) {
-		if vm.IsSimulation(ctx) {
-			// We don't support simulation.
-			return &sdk.Result{}, nil
-		} else {
-			// The simulation was done, so now allow infinite gas.
-			ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-		}
-
 		switch msg := msg.(type) {
 		default:
 			errMsg := fmt.Sprintf("Unrecognized vbank Msg type: %T", msg)
diff --git a/golang/cosmos/x/vbank/keeper/keeper.go b/golang/cosmos/x/vbank/keeper/keeper.go
index 7e33c38cced..806a860bd04 100644
--- a/golang/cosmos/x/vbank/keeper/keeper.go
+++ b/golang/cosmos/x/vbank/keeper/keeper.go
@@ -20,7 +20,7 @@ type Keeper struct {
 	bankKeeper       types.BankKeeper
 	feeCollectorName string
 	// CallToController dispatches a message to the controlling process
-	CallToController func(ctx sdk.Context, str string) (string, error)
+	CallToController func(ctx sdk.Context, str, simReturn string) (string, error)
 }
 
 // NewKeeper creates a new vbank Keeper instance
@@ -28,7 +28,7 @@ func NewKeeper(
 	cdc codec.Codec, key sdk.StoreKey, paramSpace paramtypes.Subspace,
 	bankKeeper types.BankKeeper,
 	feeCollectorName string,
-	callToController func(ctx sdk.Context, str string) (string, error),
+	callToController func(ctx sdk.Context, str, simReturn string) (string, error),
 ) Keeper {
 
 	// set KeyTable if it has not already been set
diff --git a/golang/cosmos/x/vbank/module.go b/golang/cosmos/x/vbank/module.go
index a28570ca960..9cc054a6341 100644
--- a/golang/cosmos/x/vbank/module.go
+++ b/golang/cosmos/x/vbank/module.go
@@ -192,7 +192,7 @@ func (am AppModule) EndBlock(ctx sdk.Context, req abci.RequestEndBlock) []abci.V
 		panic(err)
 	}
 	if bz != nil {
-		_, err := am.CallToController(ctx, string(bz))
+		_, err := am.CallToController(ctx, string(bz), "")
 		if err != nil {
 			panic(err)
 		}
diff --git a/golang/cosmos/x/vbank/vbank.go b/golang/cosmos/x/vbank/vbank.go
index b01638f73d7..34b066766a1 100644
--- a/golang/cosmos/x/vbank/vbank.go
+++ b/golang/cosmos/x/vbank/vbank.go
@@ -227,9 +227,9 @@ func (ch portHandler) Receive(ctx *vm.ControllerContext, str string) (ret string
 	return
 }
 
-func (am AppModule) CallToController(ctx sdk.Context, send string) (string, error) {
+func (am AppModule) CallToController(ctx sdk.Context, send, simReturn string) (string, error) {
 	// fmt.Println("vbank.go upcall", send)
-	reply, err := am.keeper.CallToController(ctx, send)
+	reply, err := am.keeper.CallToController(ctx, send, simReturn)
 	// fmt.Println("vbank.go upcall reply", reply, err)
 	return reply, err
 }
diff --git a/golang/cosmos/x/vbank/vbank_test.go b/golang/cosmos/x/vbank/vbank_test.go
index 4dfa79bbb93..64d9568c138 100644
--- a/golang/cosmos/x/vbank/vbank_test.go
+++ b/golang/cosmos/x/vbank/vbank_test.go
@@ -229,8 +229,8 @@ func (b *mockBank) SendCoinsFromModuleToModule(ctx sdk.Context, senderModule, re
 func makeTestKit(bank types.BankKeeper) (Keeper, sdk.Context) {
 	encodingConfig := params.MakeEncodingConfig()
 	cdc := encodingConfig.Marshaller
-	callToController := func(ctx sdk.Context, str string) (string, error) {
-		return "", nil
+	callToController := func(ctx sdk.Context, str, simReturn string) (string, error) {
+		return simReturn, nil
 	}
 
 	paramsTStoreKey := sdk.NewTransientStoreKey(paramstypes.TStoreKey)
@@ -472,9 +472,9 @@ func Test_EndBlock_Events(t *testing.T) {
 	}}
 	keeper, ctx := makeTestKit(bank)
 	msgsSent := []string{}
-	keeper.CallToController = func(ctx sdk.Context, str string) (string, error) {
+	keeper.CallToController = func(ctx sdk.Context, str, simReturn string) (string, error) {
 		msgsSent = append(msgsSent, str)
-		return "", nil
+		return simReturn, nil
 	}
 	am := NewAppModule(keeper)
 
@@ -546,9 +546,9 @@ func Test_EndBlock_Rewards(t *testing.T) {
 	}
 	keeper, ctx := makeTestKit(bank)
 	msgsSent := []string{}
-	keeper.CallToController = func(ctx sdk.Context, str string) (string, error) {
+	keeper.CallToController = func(ctx sdk.Context, str, simReturn string) (string, error) {
 		msgsSent = append(msgsSent, str)
-		return "", nil
+		return simReturn, nil
 	}
 	am := NewAppModule(keeper)
 
diff --git a/golang/cosmos/x/vibc/handler.go b/golang/cosmos/x/vibc/handler.go
index 17b7ae7d5df..371ef7616d8 100644
--- a/golang/cosmos/x/vibc/handler.go
+++ b/golang/cosmos/x/vibc/handler.go
@@ -4,7 +4,6 @@ import (
 	"encoding/json"
 	"fmt"
 
-	"github.com/Agoric/agoric-sdk/golang/cosmos/vm"
 	sdk "github.com/cosmos/cosmos-sdk/types"
 	sdkerrors "github.com/cosmos/cosmos-sdk/types/errors"
 )
@@ -12,14 +11,6 @@ import (
 // NewHandler returns a handler for "vibc" type messages.
 func NewHandler(keeper Keeper) sdk.Handler {
 	return func(ctx sdk.Context, msg sdk.Msg) (*sdk.Result, error) {
-		if vm.IsSimulation(ctx) {
-			// We don't support simulation.
-			return &sdk.Result{}, nil
-		} else {
-			// The simulation was done, so now allow infinite gas.
-			ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-		}
-
 		switch msg := msg.(type) {
 		case *MsgSendPacket:
 			return handleMsgSendPacket(ctx, keeper, msg)
@@ -62,7 +53,7 @@ func handleMsgSendPacket(ctx sdk.Context, keeper Keeper, msg *MsgSendPacket) (*s
 		return nil, sdkerrors.Wrap(sdkerrors.ErrJSONMarshal, err.Error())
 	}
 
-	_, err = keeper.CallToController(ctx, string(b))
+	_, err = keeper.CallToController(ctx, string(b), "")
 	// fmt.Fprintln(os.Stderr, "Returned from SwingSet", out, err)
 	if err != nil {
 		return nil, err
diff --git a/golang/cosmos/x/vibc/ibc.go b/golang/cosmos/x/vibc/ibc.go
index cb3cdb9baeb..2a77e97ccbc 100644
--- a/golang/cosmos/x/vibc/ibc.go
+++ b/golang/cosmos/x/vibc/ibc.go
@@ -172,9 +172,9 @@ func (ch portHandler) Receive(ctx *vm.ControllerContext, str string) (ret string
 	return
 }
 
-func (am AppModule) CallToController(ctx sdk.Context, send string) (string, error) {
+func (am AppModule) CallToController(ctx sdk.Context, send, simReturn string) (string, error) {
 	// fmt.Println("ibc.go upcall", send)
-	reply, err := am.keeper.CallToController(ctx, send)
+	reply, err := am.keeper.CallToController(ctx, send, simReturn)
 	// fmt.Println("ibc.go upcall reply", reply, err)
 	return reply, err
 }
@@ -203,14 +203,6 @@ func (am AppModule) OnChanOpenInit(
 	counterparty channeltypes.Counterparty,
 	version string,
 ) error {
-	if vm.IsSimulation(ctx) {
-		// We don't support simulation.
-		return nil
-	} else {
-		// The simulation was done, so now allow infinite gas.
-		ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-	}
-
 	event := channelOpenInitEvent{
 		Type:           "IBC_EVENT",
 		Event:          "channelOpenInit",
@@ -229,7 +221,7 @@ func (am AppModule) OnChanOpenInit(
 		return err
 	}
 
-	_, err = am.CallToController(ctx, string(bytes))
+	_, err = am.CallToController(ctx, string(bytes), "")
 	if err != nil {
 		return err
 	}
@@ -267,14 +259,6 @@ func (am AppModule) OnChanOpenTry(
 	version,
 	counterpartyVersion string,
 ) error {
-	if vm.IsSimulation(ctx) {
-		// We don't support simulation.
-		return nil
-	} else {
-		// The simulation was done, so now allow infinite gas.
-		ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-	}
-
 	event := channelOpenTryEvent{
 		Type:                "IBC_EVENT",
 		Event:               "channelOpenTry",
@@ -294,7 +278,7 @@ func (am AppModule) OnChanOpenTry(
 		return err
 	}
 
-	_, err = am.CallToController(ctx, string(bytes))
+	_, err = am.CallToController(ctx, string(bytes), "")
 	if err != nil {
 		return err
 	}
@@ -324,14 +308,6 @@ func (am AppModule) OnChanOpenAck(
 	channelID string,
 	counterpartyVersion string,
 ) error {
-	if vm.IsSimulation(ctx) {
-		// We don't support simulation.
-		return nil
-	} else {
-		// The simulation was done, so now allow infinite gas.
-		ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-	}
-
 	// We don't care if the channel was found.  If it wasn't then GetChannel
 	// returns an empty channel object that we can still use without crashing.
 	channel, _ := am.keeper.GetChannel(ctx, portID, channelID)
@@ -352,7 +328,7 @@ func (am AppModule) OnChanOpenAck(
 		return err
 	}
 
-	_, err = am.CallToController(ctx, string(bytes))
+	_, err = am.CallToController(ctx, string(bytes), "")
 	return err
 }
 
@@ -370,14 +346,6 @@ func (am AppModule) OnChanOpenConfirm(
 	portID,
 	channelID string,
 ) error {
-	if vm.IsSimulation(ctx) {
-		// We don't support simulation.
-		return nil
-	} else {
-		// The simulation was done, so now allow infinite gas.
-		ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-	}
-
 	event := channelOpenConfirmEvent{
 		Type:        "IBC_EVENT",
 		Event:       "channelOpenConfirm",
@@ -392,8 +360,7 @@ func (am AppModule) OnChanOpenConfirm(
 		return err
 	}
 
-	_, err = am.CallToController(ctx, string(bytes))
-
+	_, err = am.CallToController(ctx, string(bytes), "")
 	return err
 }
 
@@ -411,14 +378,6 @@ func (am AppModule) OnChanCloseInit(
 	portID,
 	channelID string,
 ) error {
-	if vm.IsSimulation(ctx) {
-		// We don't support simulation.
-		return nil
-	} else {
-		// The simulation was done, so now allow infinite gas.
-		ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-	}
-
 	event := channelCloseInitEvent{
 		Type:        "IBC_EVENT",
 		Event:       "channelCloseInit",
@@ -433,7 +392,7 @@ func (am AppModule) OnChanCloseInit(
 		return err
 	}
 
-	_, err = am.CallToController(ctx, string(bytes))
+	_, err = am.CallToController(ctx, string(bytes), "")
 	return err
 }
 
@@ -451,14 +410,6 @@ func (am AppModule) OnChanCloseConfirm(
 	portID,
 	channelID string,
 ) error {
-	if vm.IsSimulation(ctx) {
-		// We don't support simulation.
-		return nil
-	} else {
-		// The simulation was done, so now allow infinite gas.
-		ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-	}
-
 	event := channelCloseConfirmEvent{
 		Type:        "IBC_EVENT",
 		Event:       "channelCloseConfirm",
@@ -473,7 +424,7 @@ func (am AppModule) OnChanCloseConfirm(
 		return err
 	}
 
-	_, err = am.CallToController(ctx, string(bytes))
+	_, err = am.CallToController(ctx, string(bytes), "")
 	return err
 }
 
@@ -489,14 +440,6 @@ func (am AppModule) OnRecvPacket(
 	ctx sdk.Context,
 	packet channeltypes.Packet,
 ) exported.Acknowledgement {
-	if vm.IsSimulation(ctx) {
-		// We don't support simulation.
-		return nil
-	} else {
-		// The simulation was done, so now allow infinite gas.
-		ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-	}
-
 	// Sometimes we receive duplicate packets, just with a
 	// missing packet.TimeoutTimestamp.  This causes duplicate
 	// acks, with one of them being rejected.
@@ -518,8 +461,7 @@ func (am AppModule) OnRecvPacket(
 		return channeltypes.NewErrorAcknowledgement(err.Error())
 	}
 
-	// FIXME: Get acknowledgement data from this call.
-	_, err = am.CallToController(ctx, string(bytes))
+	_, err = am.CallToController(ctx, string(bytes), "")
 	if err != nil {
 		return channeltypes.NewErrorAcknowledgement(err.Error())
 	}
@@ -541,14 +483,6 @@ func (am AppModule) OnAcknowledgementPacket(
 	packet channeltypes.Packet,
 	acknowledgement []byte,
 ) (*sdk.Result, error) {
-	if vm.IsSimulation(ctx) {
-		// We don't support simulation.
-		return &sdk.Result{}, nil
-	} else {
-		// The simulation was done, so now allow infinite gas.
-		ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-	}
-
 	event := acknowledgementPacketEvent{
 		Type:            "IBC_EVENT",
 		Event:           "acknowledgementPacket",
@@ -563,7 +497,7 @@ func (am AppModule) OnAcknowledgementPacket(
 		return nil, err
 	}
 
-	_, err = am.CallToController(ctx, string(bytes))
+	_, err = am.CallToController(ctx, string(bytes), "")
 	if err != nil {
 		return nil, err
 	}
@@ -585,14 +519,6 @@ func (am AppModule) OnTimeoutPacket(
 	ctx sdk.Context,
 	packet channeltypes.Packet,
 ) (*sdk.Result, error) {
-	if vm.IsSimulation(ctx) {
-		// We don't support simulation.
-		return &sdk.Result{}, nil
-	} else {
-		// The simulation was done, so now allow infinite gas.
-		ctx = ctx.WithGasMeter(sdk.NewInfiniteGasMeter())
-	}
-
 	event := timeoutPacketEvent{
 		Type:        "IBC_EVENT",
 		Event:       "timeoutPacket",
@@ -606,7 +532,7 @@ func (am AppModule) OnTimeoutPacket(
 		return nil, err
 	}
 
-	_, err = am.CallToController(ctx, string(bytes))
+	_, err = am.CallToController(ctx, string(bytes), "")
 	if err != nil {
 		return nil, err
 	}
diff --git a/golang/cosmos/x/vibc/keeper/keeper.go b/golang/cosmos/x/vibc/keeper/keeper.go
index 9fa5e5dd758..44f7bdfcccf 100644
--- a/golang/cosmos/x/vibc/keeper/keeper.go
+++ b/golang/cosmos/x/vibc/keeper/keeper.go
@@ -28,7 +28,7 @@ type Keeper struct {
 	bankKeeper    bankkeeper.Keeper
 
 	// CallToController dispatches a message to the controlling process
-	CallToController func(ctx sdk.Context, str string) (string, error)
+	CallToController func(ctx sdk.Context, str, simReturn string) (string, error)
 }
 
 // NewKeeper creates a new dIBC Keeper instance
@@ -37,7 +37,7 @@ func NewKeeper(
 	channelKeeper types.ChannelKeeper, portKeeper types.PortKeeper,
 	bankKeeper bankkeeper.Keeper,
 	scopedKeeper capabilitykeeper.ScopedKeeper,
-	callToController func(ctx sdk.Context, str string) (string, error),
+	callToController func(ctx sdk.Context, str, simReturn string) (string, error),
 ) Keeper {
 
 	return Keeper{