diff --git a/openpgp.d.ts b/openpgp.d.ts
index a30cbdc6e..11a448e23 100644
--- a/openpgp.d.ts
+++ b/openpgp.d.ts
@@ -20,9 +20,9 @@ export function readPrivateKey(options: { armoredKey: string, config?: PartialCo
 export function readPrivateKey(options: { binaryKey: Uint8Array, config?: PartialConfig }): Promise<PrivateKey>;
 export function readPrivateKeys(options: { armoredKeys: string, config?: PartialConfig }): Promise<PrivateKey[]>;
 export function readPrivateKeys(options: { binaryKeys: Uint8Array, config?: PartialConfig }): Promise<PrivateKey[]>;
-export function generateKey(options: KeyOptions & { format?: 'armored' }): Promise<SerializedKeyPair<string> & { revocationCertificate: string }>;
-export function generateKey(options: KeyOptions & { format: 'binary' }): Promise<SerializedKeyPair<Uint8Array> & { revocationCertificate: string }>;
-export function generateKey(options: KeyOptions & { format: 'object' }): Promise<KeyPair & { revocationCertificate: string }>;
+export function generateKey(options: GenerateKeyOptions & { format?: 'armored' }): Promise<SerializedKeyPair<string> & { revocationCertificate: string }>;
+export function generateKey(options: GenerateKeyOptions & { format: 'binary' }): Promise<SerializedKeyPair<Uint8Array> & { revocationCertificate: string }>;
+export function generateKey(options: GenerateKeyOptions & { format: 'object' }): Promise<KeyPair & { revocationCertificate: string }>;
 export function decryptKey(options: { privateKey: PrivateKey; passphrase?: MaybeArray<string>; config?: PartialConfig }): Promise<PrivateKey>;
 export function encryptKey(options: { privateKey: PrivateKey; passphrase?: MaybeArray<string>; config?: PartialConfig }): Promise<PrivateKey>;
 export function reformatKey(options: { privateKey: PrivateKey; userIDs?: MaybeArray<UserID>; passphrase?: string; keyExpirationTime?: number; date?: Date, format?: 'armored', config?: PartialConfig }): Promise<SerializedKeyPair<string> & { revocationCertificate: string }>;
@@ -662,7 +662,7 @@ interface KeyPair {
 
 export type EllipticCurveName = 'ed25519' | 'curve25519' | 'p256' | 'p384' | 'p521' | 'secp256k1' | 'brainpoolP256r1' | 'brainpoolP384r1' | 'brainpoolP512r1';
 
-interface KeyOptions {
+interface GenerateKeyOptions {
   userIDs: MaybeArray<UserID>;
   passphrase?: string;
   type?: 'ecc' | 'rsa';
@@ -674,6 +674,7 @@ interface KeyOptions {
   format?: 'armored' | 'object' | 'binary';
   config?: PartialConfig;
 }
+export type KeyOptions = GenerateKeyOptions;
 
 interface SubkeyOptions {
   type?: 'ecc' | 'rsa';
diff --git a/src/openpgp.js b/src/openpgp.js
index 56a01c1f0..968c01ecc 100644
--- a/src/openpgp.js
+++ b/src/openpgp.js
@@ -37,7 +37,7 @@ import { checkKeyRequirements } from './key/helper';
  * @param {Object} options
  * @param {Object|Array<Object>} options.userIDs - User IDs as objects: `{ name: 'Jo Doe', email: 'info@jo.com' }`
  * @param {'ecc'|'rsa'} [options.type='ecc'] - The primary key algorithm type: ECC (default) or RSA
- * @param {String} [options.passphrase=(not protected)] - The passphrase used to encrypt the generated private key. If omitted, the key won't be encrypted.
+ * @param {String} [options.passphrase=(not protected)] - The passphrase used to encrypt the generated private key. If omitted or empty, the key won't be encrypted.
  * @param {Number} [options.rsaBits=4096] - Number of bits for RSA keys
  * @param {String} [options.curve='curve25519'] - Elliptic curve for ECC keys:
  *                                             curve25519 (default), p256, p384, p521, secp256k1,
@@ -53,7 +53,7 @@ import { checkKeyRequirements } from './key/helper';
  * @async
  * @static
  */
-export async function generateKey({ userIDs = [], passphrase = '', type = 'ecc', rsaBits = 4096, curve = 'curve25519', keyExpirationTime = 0, date = new Date(), subkeys = [{}], format = 'armored', config, ...rest }) {
+export async function generateKey({ userIDs = [], passphrase, type = 'ecc', rsaBits = 4096, curve = 'curve25519', keyExpirationTime = 0, date = new Date(), subkeys = [{}], format = 'armored', config, ...rest }) {
   config = { ...defaultConfig, ...config }; checkConfig(config);
   userIDs = toArray(userIDs);
   const unknownOptions = Object.keys(rest); if (unknownOptions.length > 0) throw new Error(`Unknown option: ${unknownOptions.join(', ')}`);
@@ -86,7 +86,7 @@ export async function generateKey({ userIDs = [], passphrase = '', type = 'ecc',
  * @param {Object} options
  * @param {PrivateKey} options.privateKey - Private key to reformat
  * @param {Object|Array<Object>} options.userIDs - User IDs as objects: `{ name: 'Jo Doe', email: 'info@jo.com' }`
- * @param {String} [options.passphrase=(not protected)] - The passphrase used to encrypt the reformatted private key. If omitted, the key won't be encrypted.
+ * @param {String} [options.passphrase=(not protected)] - The passphrase used to encrypt the reformatted private key. If omitted or empty, the key won't be encrypted.
  * @param {Number} [options.keyExpirationTime=0 (never expires)] - Number of seconds from the key creation time after which the key expires
  * @param {Date}   [options.date] - Override the creation date of the key signatures. If the key was previously used to sign messages, it is recommended
  *                                  to set the same date as the key creation time to ensure that old message signatures will still be verifiable using the reformatted key.
@@ -97,7 +97,7 @@ export async function generateKey({ userIDs = [], passphrase = '', type = 'ecc',
  * @async
  * @static
  */
-export async function reformatKey({ privateKey, userIDs = [], passphrase = '', keyExpirationTime = 0, date, format = 'armored', config, ...rest }) {
+export async function reformatKey({ privateKey, userIDs = [], passphrase, keyExpirationTime = 0, date, format = 'armored', config, ...rest }) {
   config = { ...defaultConfig, ...config }; checkConfig(config);
   userIDs = toArray(userIDs);
   const unknownOptions = Object.keys(rest); if (unknownOptions.length > 0) throw new Error(`Unknown option: ${unknownOptions.join(', ')}`);
diff --git a/src/packet/secret_key.js b/src/packet/secret_key.js
index c1ef8c3e5..016fbd4f4 100644
--- a/src/packet/secret_key.js
+++ b/src/packet/secret_key.js
@@ -275,11 +275,8 @@ class SecretKeyPacket extends PublicKeyPacket {
       throw new Error('Key packet is already encrypted');
     }
 
-    if (this.isDecrypted() && !passphrase) {
-      this.s2kUsage = 0;
-      return;
-    } else if (!passphrase) {
-      throw new Error('The key must be decrypted before removing passphrase protection.');
+    if (!passphrase) {
+      throw new Error('A non-empty passphrase is required for key encryption.');
     }
 
     this.s2k = new S2K(config);
diff --git a/test/general/openpgp.js b/test/general/openpgp.js
index eb3793332..3f5aadd8b 100644
--- a/test/general/openpgp.js
+++ b/test/general/openpgp.js
@@ -1192,6 +1192,14 @@ module.exports = () => describe('OpenPGP.js public api tests', function() {
       expect(unlocked.isDecrypted()).to.be.true;
     });
 
+    it('should throw on empty passphrase', async function() {
+      const { privateKey } = await openpgp.generateKey({ userIDs: [{ name: 'test', email: 'test@test.com' }], format: 'object' });
+      await expect(openpgp.encryptKey({
+        privateKey,
+        passphrase: ''
+      })).to.be.rejectedWith(/passphrase is required for key encryption/);
+    });
+
     it('should support multiple passphrases', async function() {
       const { privateKey } = await openpgp.generateKey({ userIDs: [{ name: 'test', email: 'test@test.com' }], format: 'object' });
       const passphrases = ['123', '456'];