diff --git a/blkmaker.c b/blkmaker.c
index 2a6eaf3..722a9a1 100644
--- a/blkmaker.c
+++ b/blkmaker.c
@@ -50,8 +50,7 @@ uint64_t blkmk_init_generation3(blktemplate_t * const tmpl, const void * const s
 	
 	*inout_newcb = true;
 	
-	size_t datasz = 62 + sizeof(blkheight_t) + scriptsz;
-	unsigned char *data = malloc(datasz);
+	unsigned char *data = malloc(168 + scriptsz);
 	size_t off = 0;
 	if (!data)
 		return 0;
@@ -76,6 +75,27 @@ uint64_t blkmk_init_generation3(blktemplate_t * const tmpl, const void * const s
 	data[off++] = h;
 	data[42] = data[41] - 1;
 	
+	if (tmpl->aux_count)
+	{
+		unsigned auxsz = off++;
+		data[auxsz] = 0;
+		++data[41];
+		
+		for (unsigned i = 0; i < tmpl->aux_count; ++i)
+		{
+			struct blkaux_t * const aux = &tmpl->auxs[i];
+			if ((size_t)data[41] + aux->datasz > 100)
+			{
+				free(data);
+				return 0;
+			}
+			memcpy(&data[off], tmpl->auxs[i].data, aux->datasz);
+			data[41] += aux->datasz;
+			data[auxsz] += aux->datasz;
+			off += aux->datasz;
+		}
+	}
+	
 	memcpy(&data[off],
 			"\xff\xff\xff\xff"  // sequence
 		"\x01"        // output count
diff --git a/blkmaker_jansson.c b/blkmaker_jansson.c
index 2144846..5ba24d6 100644
--- a/blkmaker_jansson.c
+++ b/blkmaker_jansson.c
@@ -226,7 +226,26 @@ const char *blktmpl_add_jansson(blktemplate_t *tmpl, const json_t *json, time_t
 			return s;
 	}
 	
-	// TODO: coinbaseaux
+	if ((v = json_object_get(json, "coinbaseaux")) && json_is_object(v))
+	{
+		tmpl->aux_count = json_object_size(v);
+		tmpl->auxs = malloc(tmpl->aux_count * sizeof(*tmpl->auxs));
+		unsigned i = 0;
+		for (void *iter = json_object_iter(v); iter; (iter = json_object_iter_next(v, iter)), ++i)
+		{
+			v2 = json_object_iter_value(iter);
+			s = json_string_value(v2);
+			if (!s)
+				continue;
+			size_t sz = strlen(s) / 2;
+			tmpl->auxs[i] = (struct blkaux_t){
+				.auxname = strdup(json_object_iter_key(iter)),
+				.data = malloc(sz),
+				.datasz = sz,
+			};
+			my_hex2bin(tmpl->auxs[i].data, s, sz);
+		}
+	}
 	
 	if ((v = json_object_get(json, "mutable")) && json_is_array(v))
 	{
diff --git a/blktemplate.c b/blktemplate.c
index 83d8292..abf2d04 100644
--- a/blktemplate.c
+++ b/blktemplate.c
@@ -101,6 +101,12 @@ void _blktxn_free(struct blktxn_t *bt) {
 }
 #define blktxn_free  _blktxn_free
 
+static
+void blkaux_clean(struct blkaux_t * const aux) {
+	free(aux->auxname);
+	free(aux->data);
+}
+
 void blktmpl_free(blktemplate_t *tmpl) {
 	for (unsigned long i = 0; i < tmpl->txncount; ++i)
 		blktxn_free(&tmpl->txns[i]);
@@ -114,6 +120,9 @@ void blktmpl_free(blktemplate_t *tmpl) {
 	// TODO: maybe free auxnames[0..n]? auxdata too
 	free(tmpl->auxnames);
 	free(tmpl->auxdata);
+	for (unsigned i = 0; i < tmpl->aux_count; ++i)
+		blkaux_clean(&tmpl->auxs[i]);
+	free(tmpl->auxs);
 	free(tmpl->workid);
 	free(tmpl->lp.id);
 	free(tmpl->lp.uri);
diff --git a/blktemplate.h b/blktemplate.h
index a931052..9e1f113 100644
--- a/blktemplate.h
+++ b/blktemplate.h
@@ -40,6 +40,12 @@ struct blktxn_t {
 	txnhash_t *hash_;
 };
 
+struct blkaux_t {
+	char *auxname;
+	unsigned char *data;
+	uint8_t datasz;
+};
+
 // BIP 23: Long Polling
 struct blktmpl_longpoll_req {
 	char *id;
@@ -100,6 +106,8 @@ typedef struct {
 	
 	time_t _time_rcvd;
 	blktime_t curtime;
+	
+	// NOTE: These were never populated nor used, see aux_count and auxs
 	char auxcount;
 	char **auxnames;
 	unsigned char **auxdata;
@@ -128,6 +136,9 @@ typedef struct {
 	int _mrklbranchcount;
 	libblkmaker_hash_t _mrklroot;
 	unsigned int next_dataid;
+	
+	unsigned aux_count;
+	struct blkaux_t *auxs;
 } blktemplate_t;
 
 extern blktemplate_t *blktmpl_create();