diff --git a/test/regression.js b/test/regression.js
index c76e3edd2..926dc7b0c 100644
--- a/test/regression.js
+++ b/test/regression.js
@@ -42,13 +42,14 @@ const runTests = async (list) => {
     await page.goto(`http://localhost:5000/optimized/${name}`);
     const optimizedBufferPromise = page.screenshot(screenshotOptions);
 
+    const writeDiffs = process.env.NO_DIFF == null;
+    const diff = writeDiffs && new PNG({ width, height });
     const originalPng = PNG.sync.read(originalBuffer);
     const optimizedPng = PNG.sync.read(await optimizedBufferPromise);
-    const diff = new PNG({ width, height });
     const matched = pixelmatch(
       originalPng.data,
       optimizedPng.data,
-      diff.data,
+      diff ? diff.data : null,
       width,
       height,
     );
@@ -59,7 +60,7 @@ const runTests = async (list) => {
     } else {
       mismatched++;
       console.error(`${name} is mismatched`);
-      if (process.env.NO_DIFF == null) {
+      if (diff) {
         const file = path.join(
           __dirname,
           'regression-diffs',