diff --git a/README.md b/README.md
index d10da68..ccf065e 100644
--- a/README.md
+++ b/README.md
@@ -85,6 +85,7 @@ These props are required to instantiate an instance of JW Player:
   * Must be a url to a jwplayer web player library. Required if jwplayer library not already instantiated on page (ie. if window.jwplayer is undefined).
   * Type: `string`
   * Example: `https://content.jwplatform.com/libraries/abcd1234.js`
+  * If you load the library yourself — a `<script>` tag in your HTML, or a Next.js `<Script>` — you can omit this prop. The component then waits up to 10 seconds for `window.jwplayer` to appear, so a player that mounts before your script finishes still sets up. If it never appears, the component logs an error and creates no player.
   <br>
 * `playlist` OR `file` OR `advertising` block with `oustream: true`
   * Player will require content in order to instantiate. See more [here](https://developer.jwplayer.com/jwplayer/docs/jw8-player-configuration-reference).
diff --git a/src/util.js b/src/util.js
index f552a5d..6a2e3f0 100644
--- a/src/util.js
+++ b/src/util.js
@@ -37,9 +37,43 @@ export function createPlayerLoadPromise(url) {
 // can be retried.
 const loadPromises = new Map();
 
+// How long to wait for a library the consumer loads themselves before giving up.
+export const EXTERNAL_LIBRARY_TIMEOUT_MS = 10000;
+const EXTERNAL_LIBRARY_POLL_MS = 50;
+
+// window.jwplayer must be callable, not merely present: a library script that is
+// still executing, or a placeholder left by another integration, would otherwise
+// be mistaken for a ready player and fail inside setup().
+function isLibraryReady() {
+  return typeof window.jwplayer === 'function';
+}
+
+// Without a library prop the consumer loads the script themselves — a Next.js
+// <Script>, a tag in index.html — and that script can still be pending when a
+// player mounts. Nothing fires an event when window.jwplayer is assigned, so
+// poll for it instead of failing the mount outright.
+function waitForExternalLibrary() {
+  return new Promise((resolve, reject) => {
+    const deadline = Date.now() + EXTERNAL_LIBRARY_TIMEOUT_MS;
+    const poll = setInterval(() => {
+      if (isLibraryReady()) {
+        clearInterval(poll);
+        resolve();
+        return;
+      }
+
+      if (Date.now() >= deadline) {
+        clearInterval(poll);
+        reject(new Error('jwplayer-react requires either a library prop, or a library script. Waited '
+          + `${EXTERNAL_LIBRARY_TIMEOUT_MS}ms for window.jwplayer and it was never defined.`));
+      }
+    }, EXTERNAL_LIBRARY_POLL_MS);
+  });
+}
+
 export function loadPlayer(url) {
-  if (!window.jwplayer && !url) throw new Error('jwplayer-react requires either a library prop, or a library script');
-  if (window.jwplayer) return Promise.resolve();
+  if (isLibraryReady()) return Promise.resolve();
+  if (!url) return waitForExternalLibrary();
 
   const pending = loadPromises.get(url);
   if (pending && pending.script.isConnected) {
diff --git a/test/jwplayer-react.test.js b/test/jwplayer-react.test.js
index a78c314..3119458 100644
--- a/test/jwplayer-react.test.js
+++ b/test/jwplayer-react.test.js
@@ -5,7 +5,7 @@
 import React from 'react';
 import { render, act } from '@testing-library/react';
 import JWPlayer from '../src/jwplayer';
-import { loadPlayer } from '../src/util';
+import { loadPlayer, EXTERNAL_LIBRARY_TIMEOUT_MS } from '../src/util';
 import { mockLibrary, players } from './util';
 
 const noop = () => {};
@@ -21,6 +21,7 @@ afterEach(() => {
     window.jwplayer = null;
     document.querySelectorAll('script').forEach((script) => script.remove());
     jest.restoreAllMocks();
+    jest.useRealTimers();
 });
 
 const createMountedComponent = async (props = {}) => {
@@ -63,9 +64,17 @@ describe('setup', () => {
         checkTests();
     });
 
-    it('Errors with no library and falsey window.jwplayer', () => {
+    // Used to throw synchronously. It now waits for a library the consumer loads
+    // themselves, so the same error arrives as a rejection after the timeout.
+    it('Errors with no library and falsey window.jwplayer', async () => {
+        jest.useFakeTimers();
         window.jwplayer = null;
-        expect(() => loadPlayer()).toThrow("jwplayer-react requires either a library prop, or a library script");
+
+        const rejection = expect(loadPlayer()).rejects
+            .toThrow('jwplayer-react requires either a library prop, or a library script');
+        jest.advanceTimersByTime(EXTERNAL_LIBRARY_TIMEOUT_MS + 100);
+
+        await rejection;
     });
 
     it('creates a script tag when mounted if window.jwplayer is not defined', () => {
@@ -412,3 +421,87 @@ describe('methods', () => {
         });
     });
 });
+
+// A library the consumer loads themselves can still be pending at mount.
+// See https://github.com/jwplayer/jwplayer-react/issues/12
+describe('externally loaded library', () => {
+    it('waits for window.jwplayer and sets up once it appears', async () => {
+        jest.useFakeTimers();
+        window.jwplayer = null;
+        const ref = React.createRef();
+
+        // No library prop: the consumer's own script tag has not run yet.
+        await act(async () => {
+            render(<JWPlayer ref={ref} playlist={playlist} />);
+        });
+        expect(ref.current.player).toBe(null);
+
+        window.jwplayer = mockLibrary;
+        await act(async () => {
+            jest.advanceTimersByTime(100);
+        });
+
+        expect(ref.current.player).toBe(players[ref.current.id]);
+    });
+
+    it('logs and creates no player when the external library never appears', async () => {
+        jest.useFakeTimers();
+        window.jwplayer = null;
+        const errorSpy = jest.spyOn(console, 'error').mockImplementation(() => {});
+        const ref = React.createRef();
+
+        await act(async () => {
+            render(<JWPlayer ref={ref} playlist={playlist} />);
+        });
+
+        await act(async () => {
+            jest.advanceTimersByTime(EXTERNAL_LIBRARY_TIMEOUT_MS + 100);
+        });
+
+        expect(ref.current.player).toBe(null);
+        expect(errorSpy).toHaveBeenCalled();
+    });
+
+    // Asserted against loadPlayer directly so React's own scheduler timers do
+    // not count towards the total.
+    it('stops polling once the library resolves', async () => {
+        jest.useFakeTimers();
+        window.jwplayer = null;
+
+        const pending = loadPlayer();
+        expect(jest.getTimerCount()).toBe(1);
+
+        window.jwplayer = mockLibrary;
+        jest.advanceTimersByTime(100);
+        await pending;
+
+        expect(jest.getTimerCount()).toBe(0);
+    });
+
+    it('stops polling when it gives up', async () => {
+        jest.useFakeTimers();
+        window.jwplayer = null;
+
+        const rejection = expect(loadPlayer()).rejects.toThrow('never defined');
+        jest.advanceTimersByTime(EXTERNAL_LIBRARY_TIMEOUT_MS + 100);
+        await rejection;
+
+        expect(jest.getTimerCount()).toBe(0);
+    });
+
+    // The failure reported in the issue: window.jwplayer was present but not yet
+    // callable, so setup() blew up.
+    it('does not treat a non-callable window.jwplayer as ready', async () => {
+        window.jwplayer = { partiallyInitialized: true };
+        const ref = React.createRef();
+
+        await act(async () => {
+            render(<JWPlayer ref={ref} library={library} playlist={playlist} />);
+        });
+
+        const scripts = Array.from(document.getElementsByTagName('script'))
+            .filter((tag) => tag.src === library);
+        expect(scripts.length).toBe(1);
+        expect(ref.current.player).toBe(null);
+    });
+});