diff --git a/.prettierignore b/.prettierignore
index bcb69a1d11..b0ae94d319 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -5,6 +5,8 @@ fixtures
 /packages/ses-integration-test/transform-tests/output
 /packages/test262-runner/prelude
 test262
+harness
+tmp
 
 *.html
 *.json