diff --git a/bin/dnssec/dnssec-signzone.c b/bin/dnssec/dnssec-signzone.c
index b6e7c6d181..e208979be4 100644
--- a/bin/dnssec/dnssec-signzone.c
+++ b/bin/dnssec/dnssec-signzone.c
@@ -3559,7 +3559,10 @@ main(int argc, char *argv[]) {
 		result = isc_file_mktemplate(output, tempfile, tempfilelen);
 		check_result(result, "isc_file_mktemplate");
 
-		result = isc_file_openunique(tempfile, &fp);
+		if (outputformat == dns_masterformat_text)
+			result = isc_file_openunique(tempfile, &fp);
+		else
+			result = isc_file_bopenunique(tempfile, &fp);
 		if (result != ISC_R_SUCCESS)
 			fatal("failed to open temporary output file: %s",
 			      isc_result_totext(result));