diff --git a/setup/management.sh b/setup/management.sh
index 7fd844ea..fb359cd3 100755
--- a/setup/management.sh
+++ b/setup/management.sh
@@ -54,7 +54,7 @@ hide_output $venv/bin/pip install --upgrade \
 # Create a backup directory and a random key for encrypting backups.
 mkdir -p "$STORAGE_ROOT/backup"
 if [ ! -f "$STORAGE_ROOT/backup/secret_key.txt" ]; then
-	umask 077; openssl rand -base64 2048 > "$STORAGE_ROOT/backup/secret_key.txt"
+	(umask 077; openssl rand -base64 2048 > "$STORAGE_ROOT/backup/secret_key.txt")
 fi