diff --git a/lib/dns/tests/rbt_serialize_test.c b/lib/dns/tests/rbt_serialize_test.c
index 8a86d49985..edfa711a32 100644
--- a/lib/dns/tests/rbt_serialize_test.c
+++ b/lib/dns/tests/rbt_serialize_test.c
@@ -130,7 +130,7 @@ static isc_result_t
 write_data(FILE *file, unsigned char *datap, void *arg, uint64_t *crc) {
 	isc_result_t result;
 	size_t ret = 0;
-	data_holder_t *data = (data_holder_t *)datap;
+	data_holder_t *data;
 	data_holder_t temp;
 	off_t where;
 
@@ -138,7 +138,8 @@ write_data(FILE *file, unsigned char *datap, void *arg, uint64_t *crc) {
 
 	REQUIRE(file != NULL);
 	REQUIRE(crc != NULL);
-	REQUIRE(data != NULL);
+	REQUIRE(datap != NULL);
+	data = (data_holder_t *)datap;
 	REQUIRE((data->len == 0 && data->data == NULL) ||
 		(data->len != 0 && data->data != NULL));