diff --git a/tests/parity/visual/screenshot-diff.ts b/tests/parity/visual/screenshot-diff.ts
index f4a0a2c3..a4981daf 100644
--- a/tests/parity/visual/screenshot-diff.ts
+++ b/tests/parity/visual/screenshot-diff.ts
@@ -137,10 +137,10 @@ function alignAndDiff(
       for (let x = 0; x < src.width; x++) {
         const srcIdx = (y * src.width + x) * 4;
         const dstIdx = (y * width + x) * 4;
-        out.data[dstIdx] = src.data[srcIdx];
-        out.data[dstIdx + 1] = src.data[srcIdx + 1];
-        out.data[dstIdx + 2] = src.data[srcIdx + 2];
-        out.data[dstIdx + 3] = src.data[srcIdx + 3];
+        out.data[dstIdx] = src.data[srcIdx]!;
+        out.data[dstIdx + 1] = src.data[srcIdx + 1]!;
+        out.data[dstIdx + 2] = src.data[srcIdx + 2]!;
+        out.data[dstIdx + 3] = src.data[srcIdx + 3]!;
       }
     }
     return PNG.sync.write(out);