diff --git a/packages/cosmwasm-stargate/src/aminotypes.spec.ts b/packages/cosmwasm-stargate/src/aminotypes.spec.ts
index d6d2de45..31f4e30f 100644
--- a/packages/cosmwasm-stargate/src/aminotypes.spec.ts
+++ b/packages/cosmwasm-stargate/src/aminotypes.spec.ts
@@ -181,9 +181,7 @@ describe("AminoTypes", () => {
           sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
           contract: "cosmos1xy4yqngt0nlkdcenxymg8tenrghmek4nmqm28k",
           code_id: "98765",
-          msg: {
-            foo: "bar",
-          },
+          msg: toBase64(toUtf8(`{"foo":"bar"}`)),
         },
       };
       expect(aminoMsg).toEqual(expected);
@@ -338,9 +336,7 @@ describe("AminoTypes", () => {
           sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
           contract: "cosmos1xy4yqngt0nlkdcenxymg8tenrghmek4nmqm28k",
           code_id: "98765",
-          msg: {
-            foo: "bar",
-          },
+          msg: toBase64(toUtf8(`{"foo":"bar"}`)),
         },
       };
       const msg = new AminoTypes({ additions: cosmWasmTypes }).fromAmino(aminoMsg);
@@ -348,11 +344,7 @@ describe("AminoTypes", () => {
         sender: "cosmos1pkptre7fdkl6gfrzlesjjvhxhlc3r4gmmk8rs6",
         contract: "cosmos1xy4yqngt0nlkdcenxymg8tenrghmek4nmqm28k",
         codeId: Long.fromString("98765"),
-        msg: toUtf8(
-          JSON.stringify({
-            foo: "bar",
-          }),
-        ),
+        msg: toUtf8(`{"foo":"bar"}`),
       };
       expect(msg).toEqual({
         typeUrl: "/cosmwasm.wasm.v1.MsgMigrateContract",
diff --git a/packages/cosmwasm-stargate/src/aminotypes.ts b/packages/cosmwasm-stargate/src/aminotypes.ts
index 7b8393a1..202bb4a5 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, fromUtf8, toBase64, toUtf8 } from "@cosmjs/encoding";
+import { fromBase64, toBase64 } from "@cosmjs/encoding";
 import { AminoConverter, Coin } from "@cosmjs/stargate";
 import {
   MsgClearAdmin,
@@ -87,8 +87,8 @@ export interface AminoMsgMigrateContract {
     readonly contract: string;
     /** The new code */
     readonly code_id: string;
-    /** Migrate message as JavaScript object */
-    readonly msg: any;
+    /** Migrate message as base64 encoded JSON */
+    readonly msg: string;
   };
 }
 
@@ -215,7 +215,7 @@ export const cosmWasmTypes: Record<string, AminoConverter> = {
       sender: sender,
       contract: contract,
       code_id: codeId.toString(),
-      msg: JSON.parse(fromUtf8(msg)),
+      msg: toBase64(msg),
     }),
     fromAmino: ({
       sender,
@@ -226,7 +226,7 @@ export const cosmWasmTypes: Record<string, AminoConverter> = {
       sender: sender,
       contract: contract,
       codeId: Long.fromString(code_id),
-      msg: toUtf8(JSON.stringify(msg)),
+      msg: fromBase64(msg),
     }),
   },
 };
diff --git a/packages/cosmwasm-stargate/src/signingcosmwasmclient.spec.ts b/packages/cosmwasm-stargate/src/signingcosmwasmclient.spec.ts
index 7b6cf487..0bca4ead 100644
--- a/packages/cosmwasm-stargate/src/signingcosmwasmclient.spec.ts
+++ b/packages/cosmwasm-stargate/src/signingcosmwasmclient.spec.ts
@@ -282,7 +282,7 @@ describe("SigningCosmWasmClient", () => {
   });
 
   describe("migrate", () => {
-    it("can can migrate from one code ID to another", async () => {
+    it("works", async () => {
       pendingWithoutWasmd();
       const wallet = await DirectSecp256k1HdWallet.fromMnemonic(alice.mnemonic, { prefix: wasmd.prefix });
       const options = { ...defaultSigningClientOptions, prefix: wasmd.prefix };
@@ -325,6 +325,48 @@ describe("SigningCosmWasmClient", () => {
 
       client.disconnect();
     });
+
+    it("works with legacy Amino signer", async () => {
+      pendingWithoutWasmd();
+      const wallet = await Secp256k1HdWallet.fromMnemonic(alice.mnemonic, { prefix: wasmd.prefix });
+      const options = { ...defaultSigningClientOptions, prefix: wasmd.prefix };
+      const client = await SigningCosmWasmClient.connectWithSigner(wasmd.endpoint, wallet, options);
+      const { codeId: codeId1 } = await client.upload(alice.address0, getHackatom().data, defaultUploadFee);
+      const { codeId: codeId2 } = await client.upload(alice.address0, getHackatom().data, defaultUploadFee);
+      const beneficiaryAddress = makeRandomAddress();
+      const { contractAddress } = await client.instantiate(
+        alice.address0,
+        codeId1,
+        {
+          verifier: alice.address0,
+          beneficiary: beneficiaryAddress,
+        },
+        "My cool label",
+        defaultInstantiateFee,
+        { admin: alice.address0 },
+      );
+      const wasmClient = await makeWasmClient(wasmd.endpoint);
+      const { contractInfo: contractInfo1 } = await wasmClient.wasm.getContractInfo(contractAddress);
+      assert(contractInfo1);
+      expect(contractInfo1.admin).toEqual(alice.address0);
+
+      const newVerifier = makeRandomAddress();
+      await client.migrate(
+        alice.address0,
+        contractAddress,
+        codeId2,
+        { verifier: newVerifier },
+        defaultMigrateFee,
+      );
+      const { contractInfo: contractInfo2 } = await wasmClient.wasm.getContractInfo(contractAddress);
+      assert(contractInfo2);
+      expect({ ...contractInfo2 }).toEqual({
+        ...contractInfo1,
+        codeId: Long.fromNumber(codeId2, true),
+      });
+
+      client.disconnect();
+    });
   });
 
   describe("execute", () => {