diff --git a/.prettierignore b/.prettierignore
index 7b065e422..ed5b8552f 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -1,3 +1,7 @@
 # Prettier auto-commit runs with GITHUB_TOKEN (GitHub App).
 # GitHub blocks that token from creating/updating anything under .github/workflows.
 .github/workflows/**
+
+# Machine-generated by npm; its format is owned by npm, not Prettier.
+# Prettier reformatting it fights npm and makes the auto-commit run fail.
+package-lock.json