diff --git a/scripts/mutate.sh b/scripts/mutate.sh
index 954613e..c99e246 100644
--- a/scripts/mutate.sh
+++ b/scripts/mutate.sh
@@ -2,7 +2,9 @@
 set -euo pipefail
 
 root="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
-work="$(mktemp -d)"
+work="$root/tmp/mutate-work"
+rm -rf "$work"
+mkdir -p "$work"
 trap 'rm -rf "$work"' EXIT
 trap 'echo "mutate: interrupted" >&2; exit 130' INT TERM