diff --git a/src/cleartext.js b/src/cleartext.js
index 1cd29ff2..51db96f6 100644
--- a/src/cleartext.js
+++ b/src/cleartext.js
@@ -124,7 +124,7 @@ export class CleartextMessage {
 /**
  * Reads an OpenPGP cleartext signed message and returns a CleartextMessage object
  * @param {Object} options
- * @param {String | ReadableStream<String>} options.cleartextMessage - Text to be parsed
+ * @param {String} options.cleartextMessage - Text to be parsed
  * @param {Object} [options.config] - Custom configuration settings to overwrite those in [config]{@link module:config}
  * @returns {CleartextMessage} New cleartext message object.
  * @async
@@ -135,6 +135,9 @@ export async function readCleartextMessage({ cleartextMessage, config }) {
   if (!cleartextMessage) {
     throw new Error('readCleartextMessage: must pass options object containing `cleartextMessage`');
   }
+  if (!util.isString(cleartextMessage)) {
+    throw new Error('readCleartextMessage: options.cleartextMessage must be a string');
+  }
   const input = await unarmor(cleartextMessage);
   if (input.type !== enums.armor.signed) {
     throw new Error('No cleartext signed message.');
@@ -203,5 +206,8 @@ export async function createCleartextMessage({ text }) {
   if (!text) {
     throw new Error('createCleartextMessage: must pass options object containing `text`');
   }
+  if (!util.isString(text)) {
+    throw new Error('createCleartextMessage: options.text must be a string');
+  }
   return new CleartextMessage(text);
 }
diff --git a/src/key/factory.js b/src/key/factory.js
index 8ea967f4..18297c32 100644
--- a/src/key/factory.js
+++ b/src/key/factory.js
@@ -253,8 +253,8 @@ async function wrapKeyObject(secretKeyPacket, secretSubkeyPackets, options, conf
 /**
  * Reads an (optionally armored) OpenPGP key and returns a key object
  * @param {Object} options
- * @param {String | ReadableStream<String>} [options.armoredKey] - Armored key to be parsed
- * @param {Uint8Array | ReadableStream<Uint8Array>} [options.binaryKey] - Binary key to be parsed
+ * @param {String} [options.armoredKey] - Armored key to be parsed
+ * @param {Uint8Array} [options.binaryKey] - Binary key to be parsed
  * @param {Object} [options.config] - Custom configuration settings to overwrite those in [config]{@link module:config}
  * @returns {Key} Key object.
  * @async
@@ -265,6 +265,12 @@ export async function readKey({ armoredKey, binaryKey, config }) {
   if (!armoredKey && !binaryKey) {
     throw new Error('readKey: must pass options object containing `armoredKey` or `binaryKey`');
   }
+  if (armoredKey && !util.isString(armoredKey)) {
+    throw new Error('readKey: options.armoredKey must be a string');
+  }
+  if (binaryKey && !util.isUint8Array(binaryKey)) {
+    throw new Error('readKey: options.binaryKey must be a Uint8Array');
+  }
   let input;
   if (armoredKey) {
     const { type, data } = await unarmor(armoredKey, config);
@@ -283,8 +289,8 @@ export async function readKey({ armoredKey, binaryKey, config }) {
 /**
  * Reads an (optionally armored) OpenPGP key block and returns a list of key objects
  * @param {Object} options
- * @param {String | ReadableStream<String>} [options.armoredKeys] - Armored keys to be parsed
- * @param {Uint8Array | ReadableStream<Uint8Array>} [options.binaryKeys] - Binary keys to be parsed
+ * @param {String} [options.armoredKeys] - Armored keys to be parsed
+ * @param {Uint8Array} [options.binaryKeys] - Binary keys to be parsed
  * @param {Object} [options.config] - Custom configuration settings to overwrite those in [config]{@link module:config}
  * @returns {Array<Key>} Key objects.
  * @async
@@ -296,6 +302,12 @@ export async function readKeys({ armoredKeys, binaryKeys, config }) {
   if (!input) {
     throw new Error('readKeys: must pass options object containing `armoredKeys` or `binaryKeys`');
   }
+  if (armoredKeys && !util.isString(armoredKeys)) {
+    throw new Error('readKeys: options.armoredKeys must be a string');
+  }
+  if (binaryKeys && !util.isUint8Array(binaryKeys)) {
+    throw new Error('readKeys: options.binaryKeys must be a Uint8Array');
+  }
   if (armoredKeys) {
     const { type, data } = await unarmor(armoredKeys, config);
     if (type !== enums.armor.publicKey && type !== enums.armor.privateKey) {
diff --git a/src/message.js b/src/message.js
index e6d642e3..1a99207a 100644
--- a/src/message.js
+++ b/src/message.js
@@ -798,6 +798,12 @@ export async function readMessage({ armoredMessage, binaryMessage, config }) {
   if (!input) {
     throw new Error('readMessage: must pass options object containing `armoredMessage` or `binaryMessage`');
   }
+  if (armoredMessage && !util.isString(armoredMessage) && !util.isStream(armoredMessage)) {
+    throw new Error('readMessage: options.armoredMessage must be a string or stream');
+  }
+  if (binaryMessage && !util.isUint8Array(binaryMessage) && !util.isStream(binaryMessage)) {
+    throw new Error('readMessage: options.binaryMessage must be a Uint8Array or stream');
+  }
   const streamType = util.isStream(input);
   if (streamType) {
     await stream.loadStreamsPonyfill();
@@ -834,6 +840,12 @@ export async function createMessage({ text, binary, filename, date = new Date(),
   if (input === undefined) {
     throw new Error('createMessage: must pass options object containing `text` or `binary`');
   }
+  if (text && !util.isString(text) && !util.isStream(text)) {
+    throw new Error('createMessage: options.text must be a string or stream');
+  }
+  if (binary && !util.isUint8Array(binary) && !util.isStream(binary)) {
+    throw new Error('createMessage: options.binary must be a Uint8Array or stream');
+  }
   const streamType = util.isStream(input);
   if (streamType) {
     await stream.loadStreamsPonyfill();
diff --git a/src/signature.js b/src/signature.js
index ef8eb84d..c9ce147f 100644
--- a/src/signature.js
+++ b/src/signature.js
@@ -56,8 +56,8 @@ export class Signature {
 /**
  * reads an (optionally armored) OpenPGP signature and returns a signature object
  * @param {Object} options
- * @param {String | ReadableStream<String>} [options.armoredSignature] - Armored signature to be parsed
- * @param {Uint8Array | ReadableStream<Uint8Array>} [options.binarySignature] - Binary signature to be parsed
+ * @param {String} [options.armoredSignature] - Armored signature to be parsed
+ * @param {Uint8Array} [options.binarySignature] - Binary signature to be parsed
  * @param {Object} [options.config] - Custom configuration settings to overwrite those in [config]{@link module:config}
  * @returns {Signature} New signature object.
  * @async
@@ -69,6 +69,12 @@ export async function readSignature({ armoredSignature, binarySignature, config
   if (!input) {
     throw new Error('readSignature: must pass options object containing `armoredSignature` or `binarySignature`');
   }
+  if (armoredSignature && !util.isString(armoredSignature)) {
+    throw new Error('readSignature: options.armoredSignature must be a string');
+  }
+  if (binarySignature && !util.isUint8Array(binarySignature)) {
+    throw new Error('readSignature: options.binarySignature must be a Uint8Array');
+  }
   if (armoredSignature) {
     const { type, data } = await unarmor(input, config);
     if (type !== enums.armor.signature) {
diff --git a/test/general/signature.js b/test/general/signature.js
index 03184b39..42c15397 100644
--- a/test/general/signature.js
+++ b/test/general/signature.js
@@ -1434,7 +1434,7 @@ hkJiXopCSWKSlQInL1devkJJUWJmTmZeugJYlpdLAagQJM0JpsCqIQZwKgAA
   });
 
   it('Should verify cleartext message correctly when using a detached binary signature and text literal data', async function () {
-    const plaintext = util.encodeUTF8('short message\nnext line \n한국어/조선말');
+    const plaintext = 'short message\nnext line \n한국어/조선말';
     const binaryPlaintext = util.encodeUTF8(plaintext);
     const pubKey = await openpgp.readKey({ armoredKey: pub_key_arm2 });
     const privKey = await openpgp.readKey({ armoredKey: priv_key_arm2 });