diff --git a/src/backends/beamcoder.ts b/src/backends/beamcoder.ts
index 2a17919..e813e2b 100644
--- a/src/backends/beamcoder.ts
+++ b/src/backends/beamcoder.ts
@@ -243,7 +243,11 @@ export class BeamcoderExtractor extends BaseExtractor implements Extractor {
      * This is the duration of the first video stream in the file expressed in seconds.
      */
     get duration(): number {
-        return this.ptsToTime(this.#demuxer.streams[this.#streamIndex].duration);
+        const stream = this.#demuxer.streams[this.#streamIndex];
+        if (stream.duration !== null) {
+            return this.ptsToTime(stream.duration);
+        }
+        return this.ptsToTime(this.#demuxer.duration) / 1000;
     }
 
     /**
diff --git a/test/framefusion.test.ts b/test/framefusion.test.ts
index a013405..9553d21 100644
--- a/test/framefusion.test.ts
+++ b/test/framefusion.test.ts
@@ -60,7 +60,7 @@ describe('FrameFusion', () => {
         await extractor.dispose();
     });
 
-    it('can get duration', async() => {
+    it('can get duration from mp4', async() => {
         // Arrange
         const extractor = await BeamcoderExtractor.create({
             inputFileOrUrl: 'https://storage.googleapis.com/lumen5-prod-images/countTo60.mp4',
@@ -73,6 +73,19 @@ describe('FrameFusion', () => {
         await extractor.dispose();
     });
 
+    it.only('can get duration from webm', async() => {
+        // Arrange
+        const extractor = await BeamcoderExtractor.create({
+            inputFileOrUrl: 'https://storage.googleapis.com/lumen5-prod-video/anita-6uTzyZtNRKztypC.webm',
+        });
+
+        // Act and Assert
+        expect(extractor.duration).to.equal(115.248);
+
+        // Cleanup
+        await extractor.dispose();
+    });
+
     it('can get duration when audio stream is longer than video stream', async() => {
         // Arrange
         const extractor = await BeamcoderExtractor.create({