diff --git a/src/Options.ts b/src/Options.ts
index 271b0faf..42156409 100644
--- a/src/Options.ts
+++ b/src/Options.ts
@@ -31,4 +31,30 @@ type Options = Xor<
   apiEndpoint?: string;
 } & Pick<AxiosRequestConfig, 'adapter' | 'proxy' | 'socketPath' | 'timeout'>;
 
+const falsyDescriptions = new Map<any, string>([
+  [undefined, 'undefined'],
+  [null, 'null'],
+  ['', 'an empty string'],
+]);
+
+/**
+ * Returns an error message (string) similar to `"Parameter "×" is null."` if a property with the passed key exists in
+ * the passed options object, or `null` if said property does not exist.
+ */
+function describeFalsyOption(options: Options, key: keyof Options) {
+  if (key in options == false) {
+    return null;
+  }
+  return `Parameter "${key}" is ${falsyDescriptions.get(options[key]) ?? options[key]}.`;
+};
+
+/**
+ * Throws a `TypeError` if the passed options object does not contain an `apiKey` or an `accessToken`.
+ */
+export function checkCredentials(options: Options) {
+  if (!options.apiKey && !options.accessToken) {
+    throw new TypeError(describeFalsyOption(options, 'apiKey') ?? describeFalsyOption(options, 'accessToken') ?? 'Missing parameter "apiKey" or "accessToken".');
+  }
+}
+
 export default Options;
diff --git a/src/createMollieClient.ts b/src/createMollieClient.ts
index 9e83a2ce..60c70485 100644
--- a/src/createMollieClient.ts
+++ b/src/createMollieClient.ts
@@ -3,6 +3,7 @@ import { version as libraryVersion } from '../package.json';
 import caCertificates from './cacert.pem';
 import NetworkClient from './communication/NetworkClient';
 import TransformingNetworkClient, { Transformers } from './communication/TransformingNetworkClient';
+import { checkCredentials } from './Options';
 import type Options from './Options';
 
 // Transformers
@@ -70,9 +71,7 @@ export default function createMollieClient(options: Options) {
     );
   }
 
-  if (!options.apiKey && !options.accessToken) {
-    throw new TypeError('Missing parameter "apiKey" or "accessToken".');
-  }
+  checkCredentials(options);
 
   const networkClient = new NetworkClient({ ...options, libraryVersion, nodeVersion: process.version, caCertificates });
 
diff --git a/tests/unit/createMollieClient.test.ts b/tests/unit/createMollieClient.test.ts
index ee145d1f..6a40a37f 100644
--- a/tests/unit/createMollieClient.test.ts
+++ b/tests/unit/createMollieClient.test.ts
@@ -1,9 +1,19 @@
 import createMollieClient from '../..';
 
-describe('mollie', () => {
-  it('should fail when no api key is provided', () => {
+describe('createMollieClient', () => {
+  it('should fail when no credentials are provided', () => {
     // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
     // @ts-ignore
-    expect(() => createMollieClient(undefined)).toThrowError(TypeError);
+    expect(() => createMollieClient({})).toThrow('Missing parameter "apiKey" or "accessToken".');
+  });
+
+  it('should throw a descriptive error when a apiKey is set to null', () => {
+    // eslint-disable-next-line @typescript-eslint/ban-ts-ignore
+    // @ts-ignore
+    expect(() => createMollieClient({ apiKey: null })).toThrow('Parameter "apiKey" is null.');
+  });
+
+  it('should throw a descriptive error when a apiKey is set to an empty string', () => {
+    expect(() => createMollieClient({ apiKey: '' })).toThrow('Parameter "apiKey" is an empty string.');
   });
 });