diff --git a/src/webkit/wkInterceptableRequest.ts b/src/webkit/wkInterceptableRequest.ts
index e7d6728628..f12a0c8bd5 100644
--- a/src/webkit/wkInterceptableRequest.ts
+++ b/src/webkit/wkInterceptableRequest.ts
@@ -77,8 +77,15 @@ export class WKInterceptableRequest implements network.RouteDelegate {
       for (const header of Object.keys(response.headers))
         responseHeaders[header.toLowerCase()] = String(response.headers[header]);
     }
-    if (response.contentType)
+    let mimeType = base64Encoded ? 'application/octet-stream' : 'text/plain';
+    if (response.contentType) {
       responseHeaders['content-type'] = response.contentType;
+      const index = response.contentType.indexOf(';');
+      if (index !== -1)
+        mimeType = response.contentType.substring(0, index).trimEnd();
+      else
+        mimeType = response.contentType.trim();
+    }
     if (responseBody && !('content-length' in responseHeaders))
       responseHeaders['content-length'] = String(Buffer.byteLength(responseBody));
 
@@ -86,7 +93,7 @@ export class WKInterceptableRequest implements network.RouteDelegate {
       requestId: this._requestId,
       status: response.status || 200,
       statusText: network.STATUS_TEXTS[String(response.status || 200)],
-      mimeType: response.contentType || (base64Encoded ? 'application/octet-stream' : 'text/plain'),
+      mimeType,
       headers: responseHeaders,
       base64Encoded,
       content: responseBody
diff --git a/test/golden-chromium/mock-svg.png b/test/golden-chromium/mock-svg.png
new file mode 100644
index 0000000000..6b382a810d
Binary files /dev/null and b/test/golden-chromium/mock-svg.png differ
diff --git a/test/golden-firefox/mock-svg.png b/test/golden-firefox/mock-svg.png
new file mode 100644
index 0000000000..a9ee147949
Binary files /dev/null and b/test/golden-firefox/mock-svg.png differ
diff --git a/test/golden-webkit/mock-svg.png b/test/golden-webkit/mock-svg.png
new file mode 100644
index 0000000000..668e8292fa
Binary files /dev/null and b/test/golden-webkit/mock-svg.png differ
diff --git a/test/interception.spec.js b/test/interception.spec.js
index fc6173ea49..5626547673 100644
--- a/test/interception.spec.js
+++ b/test/interception.spec.js
@@ -484,6 +484,23 @@ describe('Request.fulfill', function() {
     const img = await page.$('img');
     expect(await img.screenshot()).toBeGolden(golden('mock-binary-response.png'));
   });
+  it.skip(FFOX && !HEADLESS)('should allow mocking svg with charset', async({page, server, golden}) => {
+    // Firefox headful produces a different image.
+    await page.route('**/*', route => {
+      route.fulfill({
+        contentType: 'image/svg+xml ; charset=utf-8',
+        body: '<svg width="50" height="50" version="1.1" xmlns="http://www.w3.org/2000/svg"><rect x="10" y="10" width="30" height="30" stroke="black" fill="transparent" stroke-width="5"/></svg>'
+      });
+    });
+    await page.evaluate(PREFIX => {
+      const img = document.createElement('img');
+      img.src = PREFIX + '/does-not-exist.svg';
+      document.body.appendChild(img);
+      return new Promise((f, r) => { img.onload = f; img.onerror = r; });
+    }, server.PREFIX);
+    const img = await page.$('img');
+    expect(await img.screenshot()).toBeGolden(golden('mock-svg.png'));
+  });
   it('should work with file path', async({page, server, golden}) => {
     await page.route('**/*', route => route.fulfill({ contentType: 'shouldBeIgnored', path: path.join(__dirname, 'assets', 'pptr.png') }));
     await page.evaluate(PREFIX => {