diff --git a/migration/v2.23/prepare/30-coredns-config.sh b/migration/v2.23/prepare/30-coredns-config.sh
index 931a0b92..0b75e3f9 100755
--- a/migration/v2.23/prepare/30-coredns-config.sh
+++ b/migration/v2.23/prepare/30-coredns-config.sh
@@ -5,7 +5,7 @@ set -e
 additional_error_config='consolidate 5m ".* i/o timeout$" warning'
 
 tempfile=$(mktemp)
-trap 'rm -f "$tempfile"' EXIT
+trap 'rm -f "${tempfile}"' EXIT
 
 printf "coredns_additional_error_config: |\n  %s\n" "${additional_error_config}" > "${tempfile}"