diff --git a/src/hpack-dec.c b/src/hpack-dec.c
index dfbcaff27..7c3605b68 100644
--- a/src/hpack-dec.c
+++ b/src/hpack-dec.c
@@ -30,10 +30,12 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <common/standard.h>
 #include <common/hpack-dec.h>
 #include <common/hpack-huff.h>
 #include <common/hpack-tbl.h>
 #include <common/chunk.h>
+#include <common/h2.h>
 #include <common/ist.h>
 
 #include <types/global.h>
@@ -41,8 +43,10 @@
 
 #if defined(DEBUG_HPACK)
 #define hpack_debug_printf printf
+#define hpack_debug_hexdump debug_hexdump
 #else
 #define hpack_debug_printf(...) do { } while (0)
+#define hpack_debug_hexdump(...) do { } while (0)
 #endif
 
 /* reads a varint from <raw>'s lowest <b> bits and <len> bytes max (raw included).
@@ -155,6 +159,8 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 	int must_index;
 	int ret;
 
+	hpack_debug_hexdump(stderr, "[HPACK-DEC] ", (const char *)raw, 0, len);
+
 	chunk_reset(tmp);
 	ret = 0;
 	while (len) {
@@ -173,17 +179,22 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 
 			idx = get_var_int(&raw, &len, 7);
 			if (len == (uint32_t)-1) { // truncated
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TRUNCATED;
 				goto leave;
 			}
 
+			hpack_debug_printf(" idx=%u ", idx);
+
 			if (!hpack_valid_idx(dht, idx)) {
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TOO_LARGE;
 				goto leave;
 			}
 
 			value = hpack_alloc_string(tmp, idx, hpack_idx_to_value(dht, idx));
 			if (!value.ptr) {
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TOO_LARGE;
 				goto leave;
 			}
@@ -194,6 +205,7 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 			if (!name.len) {
 				name = hpack_alloc_string(tmp, idx, hpack_idx_to_name(dht, idx));
 				if (!name.ptr) {
+					hpack_debug_printf("##ERR@%d##\n", __LINE__);
 					ret = -HPACK_ERR_TOO_LARGE;
 					goto leave;
 				}
@@ -202,17 +214,22 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 		}
 		else if (*raw >= 0x20 && *raw <= 0x3f) {
 			/* max dyn table size change */
+			hpack_debug_printf("%02x: p18: dynamic table size update : ", code);
+
 			if (ret) {
 				/* 7541#4.2.1 : DHT size update must only be at the beginning */
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TOO_LARGE;
 				goto leave;
 			}
 
 			idx = get_var_int(&raw, &len, 5);
 			if (len == (uint32_t)-1) { // truncated
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TRUNCATED;
 				goto leave;
 			}
+			hpack_debug_printf(" new len=%u\n", idx);
 			continue;
 		}
 		else if (!(*raw & (*raw - 0x10))) {
@@ -233,6 +250,7 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 
 			/* retrieve name */
 			if (!len) { // truncated
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TRUNCATED;
 				goto leave;
 			}
@@ -240,6 +258,8 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 			huff = *raw & 0x80;
 			nlen = get_var_int(&raw, &len, 7);
 			if (len == (uint32_t)-1 || len < nlen) { // truncated
+				hpack_debug_printf("##ERR@%d## (truncated): nlen=%d len=%d\n",
+				                   __LINE__, (int)nlen, (int)len);
 				ret = -HPACK_ERR_TRUNCATED;
 				goto leave;
 			}
@@ -252,6 +272,7 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 			if (huff) {
 				char *ntrash = chunk_newstr(tmp);
 				if (!ntrash) {
+					hpack_debug_printf("##ERR@%d##\n", __LINE__);
 					ret = -HPACK_ERR_TOO_LARGE;
 					goto leave;
 				}
@@ -262,12 +283,15 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 					ret = -HPACK_ERR_HUFFMAN;
 					goto leave;
 				}
+				hpack_debug_printf(" [name huff %d->%d] ", (int)name.len, (int)nlen);
+
 				tmp->len += nlen; // make room for the value
 				name = ist2(ntrash, nlen);
 			}
 
 			/* retrieve value */
 			if (!len) { // truncated
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TRUNCATED;
 				goto leave;
 			}
@@ -275,6 +299,8 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 			huff = *raw & 0x80;
 			vlen = get_var_int(&raw, &len, 7);
 			if (len == (uint32_t)-1 || len < vlen) { // truncated
+				hpack_debug_printf("##ERR@%d## : vlen=%d len=%d\n",
+				                   __LINE__, (int)vlen, (int)len);
 				ret = -HPACK_ERR_TRUNCATED;
 				goto leave;
 			}
@@ -286,6 +312,7 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 			if (huff) {
 				char *vtrash = chunk_newstr(tmp);
 				if (!vtrash) {
+					hpack_debug_printf("##ERR@%d##\n", __LINE__);
 					ret = -HPACK_ERR_TOO_LARGE;
 					goto leave;
 				}
@@ -296,6 +323,8 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 					ret = -HPACK_ERR_HUFFMAN;
 					goto leave;
 				}
+				hpack_debug_printf(" [value huff %d->%d] ", (int)value.len, (int)vlen);
+
 				tmp->len += vlen; // make room for the value
 				value = ist2(vtrash, vlen);
 			}
@@ -322,12 +351,16 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 			else
 				idx = get_var_int(&raw, &len, 4);
 
+			hpack_debug_printf(" idx=%u ", idx);
+
 			if (len == (uint32_t)-1 || !len) { // truncated
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TRUNCATED;
 				goto leave;
 			}
 
 			if (!hpack_valid_idx(dht, idx)) {
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TOO_LARGE;
 				goto leave;
 			}
@@ -336,6 +369,7 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 			huff = *raw & 0x80;
 			vlen = get_var_int(&raw, &len, 7);
 			if (len == (uint32_t)-1 || len < vlen) { // truncated
+				hpack_debug_printf("##ERR@%d##\n", __LINE__);
 				ret = -HPACK_ERR_TRUNCATED;
 				goto leave;
 			}
@@ -347,13 +381,16 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 			if (huff) {
 				char *vtrash = chunk_newstr(tmp);
 				if (!vtrash) {
+					hpack_debug_printf("##ERR@%d##\n", __LINE__);
 					ret = -HPACK_ERR_TOO_LARGE;
 					goto leave;
 				}
 
 				vlen = huff_dec((const uint8_t *)value.ptr, value.len, vtrash, tmp->size - tmp->len);
 				if (vlen == (uint32_t)-1) {
-					hpack_debug_printf("1: can't decode huffman.\n");
+					hpack_debug_printf("##ERR@%d## can't decode huffman : ilen=%d osize=%d\n",
+					                   __LINE__, (int)value.len, (int)(tmp->size - tmp->len));
+					hpack_debug_hexdump(stderr, "[HUFFMAN] ", value.ptr, 0, value.len);
 					ret = -HPACK_ERR_HUFFMAN;
 					goto leave;
 				}
@@ -368,6 +405,7 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 			if (!name.len) {
 				name = hpack_alloc_string(tmp, idx, hpack_idx_to_name(dht, idx));
 				if (!name.ptr) {
+					hpack_debug_printf("##ERR@%d##\n", __LINE__);
 					ret = -HPACK_ERR_TOO_LARGE;
 					goto leave;
 				}
@@ -382,6 +420,7 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 		 *   - name.ptr != NULL || must_index : general header, unknown pseudo-header or index needed
 		 */
 		if (ret >= list_size) {
+			hpack_debug_printf("##ERR@%d##\n", __LINE__);
 			ret = -HPACK_ERR_TOO_LARGE;
 			goto leave;
 		}
@@ -397,11 +436,11 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 		}
 
 		hpack_debug_printf("\e[1;34m%s\e[0m: ",
-		                   istpad(trash.str, name.ptr ? name : hpack_idx_to_name(dht, idx)).ptr);
+				   name.ptr ? istpad(trash.str, name).ptr : h2_phdr_to_str(name.len));
 
-		hpack_debug_printf("\e[1;35m%s\e[0m [idx=%d, used=%d]\n",
-		                   istpad(trash.str, value).ptr,
-		                   must_index, dht->used);
+		hpack_debug_printf("\e[1;35m%s\e[0m [mustidx=%d, used=%d] [n=(%p,%d) v=(%p,%d)]\n",
+				   istpad(trash.str, value).ptr, must_index, dht->used,
+				   name.ptr, (int)name.len, value.ptr, (int)value.len);
 	}
 
 	if (ret >= list_size) {
@@ -414,5 +453,6 @@ int hpack_decode_frame(struct hpack_dht *dht, const uint8_t *raw, uint32_t len,
 	ret++;
 
  leave:
+	hpack_debug_printf("-- done: ret=%d list_size=%d --\n", (int)ret, (int)list_size);
 	return ret;
 }