diff --git a/blkmaker.c b/blkmaker.c
index f4710cd..d5d84cf 100644
--- a/blkmaker.c
+++ b/blkmaker.c
@@ -24,14 +24,11 @@ bool dblsha256(void *hash, const void *data, size_t datasz) {
 }
 
 static
-bool build_merkle_root(unsigned char *mrklroot_out, blktemplate_t *tmpl) {
-	if (!tmpl->cbtxn)
-		return false;
-	
+bool build_merkle_root(unsigned char *mrklroot_out, blktemplate_t *tmpl, unsigned char *cbtxndata, size_t cbtxndatasz) {
 	size_t hashcount = tmpl->txncount + 1;
 	unsigned char hashes[(hashcount + 1) * 32];
 	
-	if (!dblsha256(&hashes[0], tmpl->cbtxn->data, tmpl->cbtxn->datasz))
+	if (!dblsha256(&hashes[0], cbtxndata, cbtxndatasz))
 		return false;
 	for (int i = 0; i < tmpl->txncount; ++i)
 		if (!dblsha256(&hashes[32 * (i + 1)], tmpl->txns[i].data, tmpl->txns[i].datasz))
@@ -56,7 +53,31 @@ bool build_merkle_root(unsigned char *mrklroot_out, blktemplate_t *tmpl) {
 	return true;
 }
 
-size_t blkmk_get_data(blktemplate_t *tmpl, void *buf, size_t bufsz, time_t usetime, int16_t *out_expire) {
+static const int cbScriptSigLen = 4 + 1 + 36;
+
+bool _blkmk_extranonce(void *vout, void *vin, size_t insz, unsigned int workid) {
+	unsigned char *out = vout;
+	unsigned char *in = vin;
+	
+	if (in[cbScriptSigLen] > 100 - sizeof(workid))
+		return false;
+	
+	int cbPostScriptSig = cbScriptSigLen + 1 + in[cbScriptSigLen];
+	
+	memcpy(out, in, cbPostScriptSig+1);
+	out[cbScriptSigLen] += sizeof(workid);
+	
+	unsigned char *outPostScriptSig = &out[cbPostScriptSig];
+	unsigned int *outExtranonce = (void*)outPostScriptSig;
+	outPostScriptSig += sizeof(workid);
+	*outExtranonce = workid;
+	
+	memcpy(outPostScriptSig, &in[cbPostScriptSig], insz - cbPostScriptSig);
+	
+	return true;
+}
+
+size_t blkmk_get_data(blktemplate_t *tmpl, void *buf, size_t bufsz, time_t usetime, int16_t *out_expire, unsigned int *out_dataid) {
 	if (!(blkmk_time_left(tmpl, usetime) && blkmk_work_left(tmpl)))
 		return 0;
 	if (bufsz < 76)
@@ -66,8 +87,21 @@ size_t blkmk_get_data(blktemplate_t *tmpl, void *buf, size_t bufsz, time_t useti
 	
 	my_htole32(&cbuf[0], tmpl->version);
 	memcpy(&cbuf[4], &tmpl->prevblk, 32);
-	if (!build_merkle_root(&cbuf[36], tmpl))
+	
+	unsigned char cbtxndata[tmpl->cbtxn->datasz + sizeof(*out_dataid)];
+	size_t cbtxndatasz = tmpl->cbtxn->datasz;
+	*out_dataid = tmpl->next_dataid++;
+	if (*out_dataid)
+	{
+		if (!_blkmk_extranonce(cbtxndata, tmpl->cbtxn->data, tmpl->cbtxn->datasz, *out_dataid))
+			return 0;
+		cbtxndatasz += sizeof(*out_dataid);
+	}
+	else
+		memcpy(cbtxndata, tmpl->cbtxn->data, cbtxndatasz);
+	if (!build_merkle_root(&cbuf[36], tmpl, cbtxndata, cbtxndatasz))
 		return 0;
+	
 	blktime_t timehdr = tmpl->curtime + difftime(usetime, tmpl->_time_rcvd);
 	if (timehdr > tmpl->maxtime)
 		timehdr = tmpl->maxtime;
@@ -89,8 +123,10 @@ blktime_diff_t blkmk_time_left(const blktemplate_t *tmpl, time_t nowtime) {
 }
 
 unsigned long blkmk_work_left(const blktemplate_t *tmpl) {
-	// TODO
-	// TEMPORARY HACK
-	return (tmpl->version && !tmpl->_mrklroot[0]) ? 1 : 0;
+	if (!tmpl->version)
+		return 0;
+	if (!(tmpl->mutations & (BMM_CBAPPEND | BMM_CBSET)))
+		return 1;
+	return UINT_MAX - tmpl->next_dataid;
 	return BLKMK_UNLIMITED_WORK_COUNT;
 }
diff --git a/blkmaker.h b/blkmaker.h
index 3a78451..1f95d0a 100644
--- a/blkmaker.h
+++ b/blkmaker.h
@@ -10,7 +10,7 @@
 
 extern bool (*blkmk_sha256_impl)(void *hash_out, const void *data, size_t datasz);
 
-extern size_t blkmk_get_data(blktemplate_t *, void *buf, size_t bufsz, time_t usetime, int16_t *out_expire);
+extern size_t blkmk_get_data(blktemplate_t *, void *buf, size_t bufsz, time_t usetime, int16_t *out_expire, unsigned int *out_dataid);
 extern blktime_diff_t blkmk_time_left(const blktemplate_t *, time_t nowtime);
 extern unsigned long blkmk_work_left(const blktemplate_t *);
 #define BLKMK_UNLIMITED_WORK_COUNT  ULONG_MAX
diff --git a/blkmaker_jansson.c b/blkmaker_jansson.c
index dbe83a5..695ed1f 100644
--- a/blkmaker_jansson.c
+++ b/blkmaker_jansson.c
@@ -267,18 +267,23 @@ void my_bin2hex(char *out, const void *data, size_t datasz) {
 	}
 }
 
-json_t *blkmk_submit_jansson(blktemplate_t *tmpl, const unsigned char *data, blknonce_t nonce) {
+json_t *blkmk_submit_jansson(blktemplate_t *tmpl, const unsigned char *data, unsigned int dataid, blknonce_t nonce) {
 	unsigned char blk[80 + 8 + 1000000];
 	memcpy(blk, data, 76);
 	*(uint32_t*)(&blk[76]) = htonl(nonce);
 	size_t offs = 80;
 	
-	if (!(tmpl->mutations & BMAb_TRUNCATE))
+	if (!(tmpl->mutations & BMAb_TRUNCATE && !dataid))
 	{
 		offs += varintEncode(&blk[offs], 1 + tmpl->txncount);
 		
 		memcpy(&blk[offs], tmpl->cbtxn->data, tmpl->cbtxn->datasz);
 		offs += tmpl->cbtxn->datasz;
+		if (dataid)
+		{
+			*(int*)&blk[offs] = dataid;
+			offs += sizeof(dataid);
+		}
 		
 		if (!(tmpl->mutations & BMAb_COINBASE))
 			for (int i = 0; i < tmpl->txncount; ++i)
diff --git a/blkmaker_jansson.h b/blkmaker_jansson.h
index 4a0a872..9830283 100644
--- a/blkmaker_jansson.h
+++ b/blkmaker_jansson.h
@@ -7,6 +7,6 @@
 
 extern json_t *blktmpl_request_jansson(gbt_capabilities_t extracaps);
 extern const char *blktmpl_add_jansson(blktemplate_t *, const json_t *, time_t time_rcvd);
-extern json_t *blkmk_submit_jansson(blktemplate_t *, const unsigned char *data, blknonce_t);
+extern json_t *blkmk_submit_jansson(blktemplate_t *, const unsigned char *data, unsigned int dataid, blknonce_t);
 
 #endif
diff --git a/blktemplate.c b/blktemplate.c
index 36ad0f0..016a2a3 100644
--- a/blktemplate.c
+++ b/blktemplate.c
@@ -67,7 +67,7 @@ gbt_capabilities_t blktmpl_addcaps(const blktemplate_t *tmpl) {
 	// For now, it's a simple "filled" vs "not filled"
 	if (tmpl->version)
 		return 0;
-	return GBT_CBTXN | GBT_WORKID | BMM_TIMEINC;
+	return GBT_CBTXN | GBT_WORKID | BMM_TIMEINC | BMM_CBAPPEND;
 }
 
 static
diff --git a/blktemplate.h b/blktemplate.h
index da737a4..1cf7405 100644
--- a/blktemplate.h
+++ b/blktemplate.h
@@ -111,6 +111,7 @@ typedef struct {
 	
 	// TEMPORARY HACK
 	libblkmaker_hash_t _mrklroot;
+	unsigned int next_dataid;
 } blktemplate_t;
 
 extern blktemplate_t *blktmpl_create();
diff --git a/example.c b/example.c
index 1ae95cf..a98332e 100644
--- a/example.c
+++ b/example.c
@@ -60,10 +60,11 @@ int main(int argc, char**argv) {
 	{
 		unsigned char data[80], hash[32];
 		size_t datasz;
+		unsigned int dataid;
 		uint32_t nonce;
 		
-		datasz = blkmk_get_data(tmpl, data, sizeof(data), time(NULL), NULL);
-		assert(datasz <= sizeof(data));
+		datasz = blkmk_get_data(tmpl, data, sizeof(data), time(NULL), NULL, &dataid);
+		assert(datasz >= 76 && datasz <= sizeof(data));
 		
 		// mine the right nonce
 		// this is iterating in native order, even though SHA256 is big endian, because we don't implement noncerange
@@ -84,7 +85,7 @@ int main(int argc, char**argv) {
 		printf("Found nonce: 0x%8" PRIx32 " \n", nonce);
 		nonce = ntohl(nonce);
 		
-		req = blkmk_submit_jansson(tmpl, data, nonce);
+		req = blkmk_submit_jansson(tmpl, data, dataid, nonce);
 		assert(req);
 		// send req to server
 		send_json(req);