- dkim_sign_headers_expanded = expand_string(dkim_sign_headers);
- if (dkim_sign_headers_expanded == NULL) {
- log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
- "dkim_sign_headers: %s", expand_string_message);
- rc = NULL;
- goto CLEANUP;
+ if (dkim_sign_headers) {
+ dkim_sign_headers_expanded = expand_string(dkim_sign_headers);
+ if (dkim_sign_headers_expanded == NULL) {
+ log_write(0, LOG_MAIN|LOG_PANIC, "failed to expand "
+ "dkim_sign_headers: %s", expand_string_message);
+ rc = NULL;
+ goto CLEANUP;
+ }
+ }
+ else {
+ /* pass NULL, which means default header list */
+ dkim_sign_headers_expanded = NULL;