diff --git a/web3.js/src/connection.js b/web3.js/src/connection.js
index 50ad05466d4..b2bc7381728 100644
--- a/web3.js/src/connection.js
+++ b/web3.js/src/connection.js
@@ -713,7 +713,7 @@ const GetTokenAccountsByOwner = jsonRpcResultAndContext(
         executable: 'boolean',
         owner: 'string',
         lamports: 'number',
-        data: 'string',
+        data: ['string', struct.literal('base64')],
         rentEpoch: 'number?',
       }),
     }),
@@ -795,7 +795,7 @@ const ParsedAccountInfoResult = struct.object({
   owner: 'string',
   lamports: 'number',
   data: struct.union([
-    'string',
+    ['string', struct.literal('base64')],
     struct.pick({
       program: 'string',
       parsed: 'any',
@@ -1613,7 +1613,7 @@ export class Connection {
       _args.push({programId: filter.programId.toBase58()});
     }
 
-    const args = this._buildArgs(_args, commitment, 'binary64');
+    const args = this._buildArgs(_args, commitment, 'base64');
     const unsafeRes = await this._rpcRequest('getTokenAccountsByOwner', args);
     const res = GetTokenAccountsByOwner(unsafeRes);
     if (res.error) {
@@ -1631,15 +1631,18 @@ export class Connection {
 
     return {
       context,
-      value: value.map(result => ({
-        pubkey: new PublicKey(result.pubkey),
-        account: {
-          executable: result.account.executable,
-          owner: new PublicKey(result.account.owner),
-          lamports: result.account.lamports,
-          data: Buffer.from(result.account.data, 'base64'),
-        },
-      })),
+      value: value.map(result => {
+        assert(result.account.data[1] === 'base64');
+        return {
+          pubkey: new PublicKey(result.pubkey),
+          account: {
+            executable: result.account.executable,
+            owner: new PublicKey(result.account.owner),
+            lamports: result.account.lamports,
+            data: Buffer.from(result.account.data[0], 'base64'),
+          },
+        };
+      }),
     };
   }
 
@@ -1752,7 +1755,7 @@ export class Connection {
     const args = this._buildArgs(
       [publicKey.toBase58()],
       commitment,
-      'binary64',
+      'base64',
     );
     const unsafeRes = await this._rpcRequest('getAccountInfo', args);
     const res = GetAccountInfoAndContextRpcResult(unsafeRes);
@@ -1769,11 +1772,12 @@ export class Connection {
     let value = null;
     if (res.result.value) {
       const {executable, owner, lamports, data} = res.result.value;
+      assert(data[1] === 'base64');
       value = {
         executable,
         owner: new PublicKey(owner),
         lamports,
-        data: Buffer.from(data, 'base64'),
+        data: Buffer.from(data[0], 'base64'),
       };
     }
 
@@ -1817,7 +1821,8 @@ export class Connection {
 
       let data = resultData;
       if (!data.program) {
-        data = Buffer.from(data, 'base64');
+        assert(data[1] === 'base64');
+        data = Buffer.from(data[0], 'base64');
       }
 
       value = {
@@ -1864,7 +1869,7 @@ export class Connection {
     const args = this._buildArgs(
       [programId.toBase58()],
       commitment,
-      'binary64',
+      'base64',
     );
     const unsafeRes = await this._rpcRequest('getProgramAccounts', args);
     const res = GetProgramAccountsRpcResult(unsafeRes);
@@ -1881,13 +1886,14 @@ export class Connection {
     assert(typeof result !== 'undefined');
 
     return result.map(result => {
+      assert(result.account.data[1] === 'base64');
       return {
         pubkey: new PublicKey(result.pubkey),
         account: {
           executable: result.account.executable,
           owner: new PublicKey(result.account.owner),
           lamports: result.account.lamports,
-          data: Buffer.from(result.account.data, 'base64'),
+          data: Buffer.from(result.account.data[0], 'base64'),
         },
       };
     });
@@ -1931,7 +1937,8 @@ export class Connection {
 
       let data = resultData;
       if (!data.program) {
-        data = Buffer.from(data, 'base64');
+        assert(data[1] === 'base64');
+        data = Buffer.from(data[0], 'base64');
       }
 
       return {
@@ -2776,7 +2783,7 @@ export class Connection {
       this._subscribe(
         sub,
         'accountSubscribe',
-        this._buildArgs([sub.publicKey], sub.commitment, 'binary64'),
+        this._buildArgs([sub.publicKey], sub.commitment, 'base64'),
       );
     }
 
@@ -2785,7 +2792,7 @@ export class Connection {
       this._subscribe(
         sub,
         'programSubscribe',
-        this._buildArgs([sub.programId], sub.commitment, 'binary64'),
+        this._buildArgs([sub.programId], sub.commitment, 'base64'),
       );
     }
 
@@ -2899,6 +2906,7 @@ export class Connection {
         const {result} = res;
         const {value, context} = result;
 
+        assert(value.account.data[1] === 'base64');
         sub.callback(
           {
             accountId: value.pubkey,
@@ -2906,7 +2914,7 @@ export class Connection {
               executable: value.account.executable,
               owner: new PublicKey(value.account.owner),
               lamports: value.account.lamports,
-              data: Buffer.from(value.account.data, 'base64'),
+              data: Buffer.from(value.account.data[0], 'base64'),
             },
           },
           context,
@@ -3016,7 +3024,7 @@ export class Connection {
   _buildArgs(
     args: Array<any>,
     override: ?Commitment,
-    encoding?: 'jsonParsed' | 'binary64',
+    encoding?: 'jsonParsed' | 'base64',
   ): Array<any> {
     const commitment = override || this._commitment;
     if (commitment || encoding) {
diff --git a/web3.js/test/connection.test.js b/web3.js/test/connection.test.js
index 57f9ad2e1f4..2497f165065 100644
--- a/web3.js/test/connection.test.js
+++ b/web3.js/test/connection.test.js
@@ -63,7 +63,7 @@ test('get account info - not found', async () => {
     url,
     {
       method: 'getAccountInfo',
-      params: [account.publicKey.toBase58(), {encoding: 'binary64'}],
+      params: [account.publicKey.toBase58(), {encoding: 'base64'}],
     },
     {
       error: null,
@@ -255,7 +255,7 @@ test('get program accounts', async () => {
       method: 'getProgramAccounts',
       params: [
         programId.publicKey.toBase58(),
-        {commitment: 'recent', encoding: 'binary64'},
+        {commitment: 'recent', encoding: 'base64'},
       ],
     },
     {
@@ -263,7 +263,7 @@ test('get program accounts', async () => {
       result: [
         {
           account: {
-            data: '',
+            data: ['', 'base64'],
             executable: false,
             lamports: LAMPORTS_PER_SOL - feeCalculator.lamportsPerSignature,
             owner: programId.publicKey.toBase58(),
@@ -273,7 +273,7 @@ test('get program accounts', async () => {
         },
         {
           account: {
-            data: '',
+            data: ['', 'base64'],
             executable: false,
             lamports:
               0.5 * LAMPORTS_PER_SOL - feeCalculator.lamportsPerSignature,
@@ -1681,7 +1681,7 @@ test('request airdrop', async () => {
       method: 'getAccountInfo',
       params: [
         account.publicKey.toBase58(),
-        {commitment: 'recent', encoding: 'binary64'},
+        {commitment: 'recent', encoding: 'base64'},
       ],
     },
     {
@@ -1693,7 +1693,7 @@ test('request airdrop', async () => {
         value: {
           owner: '11111111111111111111111111111111',
           lamports: minimumAmount + 42,
-          data: '',
+          data: ['', 'base64'],
           executable: false,
         },
       },
@@ -1727,7 +1727,7 @@ test('request airdrop', async () => {
         value: {
           owner: '11111111111111111111111111111111',
           lamports: minimumAmount + 42,
-          data: '',
+          data: ['', 'base64'],
           executable: false,
         },
       },
diff --git a/web3.js/test/nonce.test.js b/web3.js/test/nonce.test.js
index 737f7f378dc..735ab7454d3 100644
--- a/web3.js/test/nonce.test.js
+++ b/web3.js/test/nonce.test.js
@@ -14,7 +14,7 @@ if (!mockRpcEnabled) {
   jest.setTimeout(30000);
 }
 
-const expectedData = (authorizedPubkey: PublicKey): string => {
+const expectedData = (authorizedPubkey: PublicKey): [string, string] => {
   const expectedData = Buffer.alloc(NONCE_ACCOUNT_LENGTH);
   expectedData.writeInt32LE(0, 0); // Version, 4 bytes
   expectedData.writeInt32LE(1, 4); // State, 4 bytes
@@ -22,7 +22,7 @@ const expectedData = (authorizedPubkey: PublicKey): string => {
   const mockNonce = new Account();
   mockNonce.publicKey.toBuffer().copy(expectedData, 40); // Hash, 32 bytes
   expectedData.writeUInt16LE(5000, 72); // feeCalculator, 8 bytes
-  return expectedData.toString('base64');
+  return [expectedData.toString('base64'), 'base64'];
 };
 
 test('create and query nonce account', async () => {
@@ -119,7 +119,10 @@ test('create and query nonce account', async () => {
     url,
     {
       method: 'getAccountInfo',
-      params: [nonceAccount.publicKey.toBase58(), {commitment: 'recent'}],
+      params: [
+        nonceAccount.publicKey.toBase58(),
+        {encoding: 'base64', commitment: 'recent'},
+      ],
     },
     {
       error: null,
@@ -243,7 +246,10 @@ test('create and query nonce account with seed', async () => {
     url,
     {
       method: 'getAccountInfo',
-      params: [noncePubkey.toBase58(), {commitment: 'recent'}],
+      params: [
+        noncePubkey.toBase58(),
+        {encoding: 'base64', commitment: 'recent'},
+      ],
     },
     {
       error: null,