diff --git a/src/tools/screenshot.ts b/src/tools/screenshot.ts
index d8d3dfcf..4312c02a 100644
--- a/src/tools/screenshot.ts
+++ b/src/tools/screenshot.ts
@@ -62,10 +62,13 @@ export const screenshot = defineTool({
       pageOrHandle = context.getSelectedPage();
     }
 
+    const format = request.params.format;
+    const quality = format === 'png' ? undefined : request.params.quality;
+
     const screenshot = await pageOrHandle.screenshot({
-      type: request.params.format,
+      type: format,
       fullPage: request.params.fullPage,
-      quality: request.params.quality,
+      quality,
       optimizeForSpeed: true, // Bonus: optimize encoding for speed
     });
 
diff --git a/tests/tools/screenshot.test.ts b/tests/tools/screenshot.test.ts
index c5b3a460..ebf207e1 100644
--- a/tests/tools/screenshot.test.ts
+++ b/tests/tools/screenshot.test.ts
@@ -30,6 +30,25 @@ describe('screenshot', () => {
         );
       });
     });
+    it('ignores quality', async () => {
+      await withBrowser(async (response, context) => {
+        const fixture = screenshots.basic;
+        const page = context.getSelectedPage();
+        await page.setContent(fixture.html);
+        await screenshot.handler(
+          {params: {format: 'png', quality: 0}},
+          response,
+          context,
+        );
+
+        assert.equal(response.images.length, 1);
+        assert.equal(response.images[0].mimeType, 'image/png');
+        assert.equal(
+          response.responseLines.at(0),
+          "Took a screenshot of the current page's viewport.",
+        );
+      });
+    });
     it('with jpeg', async () => {
       await withBrowser(async (response, context) => {
         await screenshot.handler({params: {format: 'jpeg'}}, response, context);