diff --git a/x/swingset/codec.go b/x/swingset/codec.go
index ea3824c82ba..a5a7d523e90 100644
--- a/x/swingset/codec.go
+++ b/x/swingset/codec.go
@@ -4,7 +4,10 @@ import (
 	"github.com/cosmos/cosmos-sdk/codec"
 )
 
+var ModuleCdc *codec.Codec
+
 // RegisterCodec registers concrete types on the Amino codec
 func RegisterCodec(cdc *codec.Codec) {
+	ModuleCdc = cdc
 	cdc.RegisterConcrete(MsgDeliverInbound{}, "swingset/DeliverInbound", nil)
 }
diff --git a/x/swingset/msgs.go b/x/swingset/msgs.go
index 11ada37a413..3157ff6aaa4 100644
--- a/x/swingset/msgs.go
+++ b/x/swingset/msgs.go
@@ -1,8 +1,6 @@
 package swingset
 
 import (
-	"encoding/json"
-
 	sdk "github.com/cosmos/cosmos-sdk/types"
 )
 
@@ -65,11 +63,7 @@ func (msg MsgDeliverInbound) GetSignBytes() []byte {
 	if msg.Nums == nil {
 		msg.Nums = []int{}
 	}
-	b, err := json.Marshal(msg)
-	if err != nil {
-		panic(err)
-	}
-	return sdk.MustSortJSON(b)
+	return sdk.MustSortJSON(ModuleCdc.MustMarshalJSON(msg))
 }
 
 // GetSigners defines whose signature is required