diff --git a/README.md b/README.md
index 204b458..39edcba 100644
--- a/README.md
+++ b/README.md
@@ -47,6 +47,8 @@ Most development tasks can be run directly from `npm` or via `make` wrapper reci
 | Run tests with coverage        | `npm run cover` | `make cover` |
 | Build documentation            | `npm run docs`  | `make docs`  |
 
+Note that the some of the tests require `python3` and the Python packages `matplotlib` and `Pillow` to be installed.
+
 ## 🙏 Acknowledgments
 
 Many thanks to the nteract community for [`kernelspecs`](https://github.com/nteract/kernelspecs) and
diff --git a/src/index.test.ts b/src/index.test.ts
index 1b34dad..f3e21ac 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -171,7 +171,9 @@ import sys; sys.stderr.write('An error!')
     expect(chunk.errors).toEqual([
       schema.codeError({ errorMessage: 'An error!' }),
     ])
-    expect(chunk.outputs).toEqual([])
+    expect(chunk.outputs).toEqual([
+      9, // The write() returns the number of bytes written
+    ])
   })
 
   test('errors', async () => {
@@ -269,6 +271,24 @@ describe('unbundle', () => {
     }
   })
 
+  test('vega', () => {
+    const image = jupita.unbundle({
+      'application/vnd.vegalite.v4+json': {},
+    })
+    expect(schema.isA('ImageObject', image)).toBe(true)
+    if (schema.isA('ImageObject', image)) {
+      expect(image.content).toEqual(
+        expect.arrayContaining([
+          expect.objectContaining({
+            mediaType: 'application/vnd.vegalite.v4+json',
+            spec: {},
+          }),
+        ])
+      )
+      expect(image.contentUrl).toMatch(`https://via.placeholder.com`)
+    }
+  })
+
   test.each([['image/png'], ['image/jpeg'], ['image/gif']])(
     '%s',
     (mediaType) => {
diff --git a/src/index.ts b/src/index.ts
index 571dbb8..0497b0e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -464,6 +464,27 @@ export class Jupita extends Listener {
       })
     }
 
+    for (const mediaType of [
+      'application/vnd.vega.v1+json',
+      'application/vnd.vega.v2+json',
+      'application/vnd.vega.v3+json',
+      'application/vnd.vega.v4+json',
+      'application/vnd.vega.v5+json',
+      'application/vnd.vegalite.v1+json',
+      'application/vnd.vegalite.v2+json',
+      'application/vnd.vegalite.v3+json',
+      'application/vnd.vegalite.v4+json',
+    ]) {
+      const vega = bundle[mediaType]
+      if (vega !== undefined) {
+        return schema.imageObject({
+          content: [{ mediaType, spec: vega }],
+          contentUrl:
+            'https://via.placeholder.com/400x60?text=Unable%20to%20render%20Vega%20output',
+        })
+      }
+    }
+
     for (const mediaType of ['image/png', 'image/jpeg', 'image/gif']) {
       const image = bundle[mediaType]
       if (image !== undefined) {