diff --git a/packages/cosmwasm-stargate/src/aminotypes.spec.ts b/packages/cosmwasm-stargate/src/aminotypes.spec.ts
index 31f4e30f..85739353 100644
--- a/packages/cosmwasm-stargate/src/aminotypes.spec.ts
+++ b/packages/cosmwasm-stargate/src/aminotypes.spec.ts
@@ -1,5 +1,5 @@
 /* eslint-disable @typescript-eslint/naming-convention */
-import { fromBase64, toBase64, toUtf8 } from "@cosmjs/encoding";
+import { fromBase64, toUtf8 } from "@cosmjs/encoding";
 import { AminoTypes, coins } from "@cosmjs/stargate";
 import {
   MsgClearAdmin,
@@ -64,7 +64,7 @@ describe("AminoTypes", () => {
             sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
             code_id: "12345",
             label: "sticky",
-            msg: toBase64(toUtf8(`{"foo":"bar"}`)),
+            msg: { foo: "bar" },
             funds: coins(1234, "ucosm"),
             admin: "cosmos10dyr9899g6t0pelew4nvf4j5c3jcgv0r73qga5",
           },
@@ -92,7 +92,7 @@ describe("AminoTypes", () => {
             sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
             code_id: "12345",
             label: "sticky",
-            msg: toBase64(toUtf8(`{"foo":"bar"}`)),
+            msg: { foo: "bar" },
             funds: coins(1234, "ucosm"),
             admin: undefined,
           },
@@ -157,7 +157,7 @@ describe("AminoTypes", () => {
         value: {
           sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
           contract: "cosmos1xy4yqngt0nlkdcenxymg8tenrghmek4nmqm28k",
-          msg: toBase64(toUtf8(`{"foo":"bar"}`)),
+          msg: { foo: "bar" },
           funds: coins(1234, "ucosm"),
         },
       };
@@ -181,7 +181,7 @@ describe("AminoTypes", () => {
           sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
           contract: "cosmos1xy4yqngt0nlkdcenxymg8tenrghmek4nmqm28k",
           code_id: "98765",
-          msg: toBase64(toUtf8(`{"foo":"bar"}`)),
+          msg: { foo: "bar" },
         },
       };
       expect(aminoMsg).toEqual(expected);
@@ -218,7 +218,7 @@ describe("AminoTypes", () => {
             sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
             code_id: "12345",
             label: "sticky",
-            msg: toBase64(toUtf8(`{"foo":"bar"}`)),
+            msg: { foo: "bar" },
             funds: coins(1234, "ucosm"),
             admin: "cosmos10dyr9899g6t0pelew4nvf4j5c3jcgv0r73qga5",
           },
@@ -246,7 +246,7 @@ describe("AminoTypes", () => {
             sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
             code_id: "12345",
             label: "sticky",
-            msg: toBase64(toUtf8(`{"foo":"bar"}`)),
+            msg: { foo: "bar" },
             funds: coins(1234, "ucosm"),
           },
         };
@@ -312,7 +312,7 @@ describe("AminoTypes", () => {
         value: {
           sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
           contract: "cosmos1xy4yqngt0nlkdcenxymg8tenrghmek4nmqm28k",
-          msg: toBase64(toUtf8(`{"foo":"bar"}`)),
+          msg: { foo: "bar" },
           funds: coins(1234, "ucosm"),
         },
       };
@@ -336,7 +336,7 @@ describe("AminoTypes", () => {
           sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
           contract: "cosmos1xy4yqngt0nlkdcenxymg8tenrghmek4nmqm28k",
           code_id: "98765",
-          msg: toBase64(toUtf8(`{"foo":"bar"}`)),
+          msg: { foo: "bar" },
         },
       };
       const msg = new AminoTypes({ additions: cosmWasmTypes }).fromAmino(aminoMsg);
diff --git a/packages/cosmwasm-stargate/src/aminotypes.ts b/packages/cosmwasm-stargate/src/aminotypes.ts
index 202bb4a5..b9aa88da 100644
--- a/packages/cosmwasm-stargate/src/aminotypes.ts
+++ b/packages/cosmwasm-stargate/src/aminotypes.ts
@@ -1,5 +1,5 @@
 /* eslint-disable @typescript-eslint/naming-convention */
-import { fromBase64, toBase64 } from "@cosmjs/encoding";
+import { fromBase64, fromUtf8, toBase64, toUtf8 } from "@cosmjs/encoding";
 import { AminoConverter, Coin } from "@cosmjs/stargate";
 import {
   MsgClearAdmin,
@@ -45,8 +45,8 @@ export interface AminoMsgExecuteContract {
     readonly sender: string;
     /** Bech32 account address */
     readonly contract: string;
-    /** Execute message as base64 encoded JSON */
-    readonly msg: string;
+    /** Execute message as JavaScript object */
+    readonly msg: any;
     readonly funds: readonly Coin[];
   };
 }
@@ -65,8 +65,8 @@ export interface AminoMsgInstantiateContract {
     readonly code_id: string;
     /** Human-readable label for this contract */
     readonly label: string;
-    /** Instantiate message as base64 encoded JSON */
-    readonly msg: string;
+    /** Instantiate message as JavaScript object */
+    readonly msg: any;
     readonly funds: readonly Coin[];
     /** Bech32-encoded admin address */
     readonly admin?: string;
@@ -87,8 +87,8 @@ export interface AminoMsgMigrateContract {
     readonly contract: string;
     /** The new code */
     readonly code_id: string;
-    /** Migrate message as base64 encoded JSON */
-    readonly msg: string;
+    /** Migrate message as JavaScript object */
+    readonly msg: any;
   };
 }
 
@@ -150,7 +150,7 @@ export const cosmWasmTypes: Record<string, AminoConverter> = {
       sender: sender,
       code_id: codeId.toString(),
       label: label,
-      msg: toBase64(msg),
+      msg: JSON.parse(fromUtf8(msg)),
       funds: funds,
       admin: admin || undefined,
     }),
@@ -165,7 +165,7 @@ export const cosmWasmTypes: Record<string, AminoConverter> = {
       sender: sender,
       codeId: Long.fromString(code_id),
       label: label,
-      msg: fromBase64(msg),
+      msg: toUtf8(JSON.stringify(msg)),
       funds: [...funds],
       admin: admin ?? "",
     }),
@@ -199,13 +199,13 @@ export const cosmWasmTypes: Record<string, AminoConverter> = {
     toAmino: ({ sender, contract, msg, funds }: MsgExecuteContract): AminoMsgExecuteContract["value"] => ({
       sender: sender,
       contract: contract,
-      msg: toBase64(msg),
+      msg: JSON.parse(fromUtf8(msg)),
       funds: funds,
     }),
     fromAmino: ({ sender, contract, msg, funds }: AminoMsgExecuteContract["value"]): MsgExecuteContract => ({
       sender: sender,
       contract: contract,
-      msg: fromBase64(msg),
+      msg: toUtf8(JSON.stringify(msg)),
       funds: [...funds],
     }),
   },
@@ -215,7 +215,7 @@ export const cosmWasmTypes: Record<string, AminoConverter> = {
       sender: sender,
       contract: contract,
       code_id: codeId.toString(),
-      msg: toBase64(msg),
+      msg: JSON.parse(fromUtf8(msg)),
     }),
     fromAmino: ({
       sender,
@@ -226,7 +226,7 @@ export const cosmWasmTypes: Record<string, AminoConverter> = {
       sender: sender,
       contract: contract,
       codeId: Long.fromString(code_id),
-      msg: fromBase64(msg),
+      msg: toUtf8(JSON.stringify(msg)),
     }),
   },
 };