diff --git a/src/hpack-tbl.c b/src/hpack-tbl.c
index 06798dc51..92601f3f9 100644
--- a/src/hpack-tbl.c
+++ b/src/hpack-tbl.c
@@ -111,7 +111,7 @@ static inline unsigned int hpack_dht_get_tail(const struct hpack_dht *dht)
 
 #ifdef DEBUG_HPACK
 /* dump the whole dynamic header table */
-static void hpack_dht_dump(const struct hpack_dht *dht)
+static void hpack_dht_dump(FILE *out, const struct hpack_dht *dht)
 {
 	int i;
 	unsigned int slot;
@@ -119,7 +119,7 @@ static void hpack_dht_dump(const struct hpack_dht *dht)
 
 	for (i = HPACK_SHT_SIZE; i < HPACK_SHT_SIZE + dht->used; i++) {
 		slot = (hpack_get_dte(dht, i - HPACK_SHT_SIZE + 1) - dht->dte);
-		fprintf(stderr, "idx=%d slot=%u name=<%s> value=<%s> addr=%u-%u\n",
+		fprintf(out, "idx=%d slot=%u name=<%s> value=<%s> addr=%u-%u\n",
 			i, slot,
 			istpad(name, hpack_idx_to_name(dht, i)).ptr,
 			istpad(value, hpack_idx_to_value(dht, i)).ptr,