diff --git a/.github/workflows/wpt.yml b/.github/workflows/wpt.yml
index 2011e766..fc8da414 100644
--- a/.github/workflows/wpt.yml
+++ b/.github/workflows/wpt.yml
@@ -31,7 +31,7 @@ jobs:
       - uses: ./.github/actions/install
 
       - name: json output
-        run: zig build -Dprebuilt_v8_path=v8/libc_v8.a wpt -- --json > wpt.json
+        run: zig build -Dprebuilt_v8_path=v8/libc_v8.a -Doptimize=ReleaseFast wpt -- --json > wpt.json
 
       - name: write commit
         run: |