diff --git a/web3.js/src/account.js b/web3.js/src/account.js
index 05e53a89c8..a0df039979 100644
--- a/web3.js/src/account.js
+++ b/web3.js/src/account.js
@@ -38,6 +38,6 @@ export class Account {
    * The **unencrypted** secret key for this account
    */
   get secretKey(): Buffer {
-    return this._keypair.secretKey;
+    return toBuffer(this._keypair.secretKey);
   }
 }
diff --git a/web3.js/src/publickey.js b/web3.js/src/publickey.js
index d448c4782f..c5573fa079 100644
--- a/web3.js/src/publickey.js
+++ b/web3.js/src/publickey.js
@@ -113,7 +113,7 @@ export class PublicKey {
       Buffer.from('ProgramDerivedAddress'),
     ]);
     let hash = await sha256(new Uint8Array(buffer));
-    let publicKeyBytes = new BN(hash, 16).toArray(null, 32);
+    let publicKeyBytes = new BN(hash, 16).toArray(undefined, 32);
     if (is_on_curve(publicKeyBytes)) {
       throw new Error(`Invalid seeds, address must fall off the curve`);
     }
diff --git a/web3.js/src/secp256k1-program.js b/web3.js/src/secp256k1-program.js
index 51d213c2bc..325fea2873 100644
--- a/web3.js/src/secp256k1-program.js
+++ b/web3.js/src/secp256k1-program.js
@@ -183,13 +183,20 @@ export class Secp256k1Program {
   static createInstructionWithPrivateKey(
     params: CreateSecp256k1InstructionWithPrivateKeyParams,
   ): TransactionInstruction {
-    const {privateKey, message} = params;
+    const {privateKey: pkey, message} = params;
 
     assert(
-      privateKey.length === PRIVATE_KEY_BYTES,
-      `Private key must be ${PRIVATE_KEY_BYTES} bytes but received ${privateKey.length} bytes`,
+      pkey.length === PRIVATE_KEY_BYTES,
+      `Private key must be ${PRIVATE_KEY_BYTES} bytes but received ${pkey.length} bytes`,
     );
 
+    let privateKey;
+    if (Array.isArray(pkey)) {
+      privateKey = Uint8Array.from(pkey);
+    } else {
+      privateKey = pkey;
+    }
+
     try {
       const publicKey = publicKeyCreate(privateKey, false).slice(1); // throw away leading byte
       const messageHash = Buffer.from(
diff --git a/web3.js/src/transaction.js b/web3.js/src/transaction.js
index b0f7b636f2..e79475cd46 100644
--- a/web3.js/src/transaction.js
+++ b/web3.js/src/transaction.js
@@ -11,6 +11,7 @@ import {PublicKey} from './publickey';
 import {Account} from './account';
 import * as shortvec from './util/shortvec-encoding';
 import type {Blockhash} from './blockhash';
+import {toBuffer} from './util/to-buffer';
 
 /**
  * @typedef {string} TransactionSignature
@@ -522,7 +523,7 @@ export class Transaction {
     const signData = message.serialize();
     signers.forEach(signer => {
       const signature = nacl.sign.detached(signData, signer.secretKey);
-      this._addSignature(signer.publicKey, signature);
+      this._addSignature(signer.publicKey, toBuffer(signature));
     });
   }