diff --git a/.gitignore b/.gitignore
index c2e17c6..6200e5f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -23,3 +23,4 @@ autom4te.cache
 config.*
 ii
 ar-lib
+compile
diff --git a/blkmaker.c b/blkmaker.c
index 7c51da3..4c18522 100644
--- a/blkmaker.c
+++ b/blkmaker.c
@@ -411,6 +411,17 @@ size_t blkmk_get_data(blktemplate_t *tmpl, void *buf, size_t bufsz, time_t useti
 	if (bufsz < 76)
 		return 76;
 	
+	if (tmpl->cbtxn->datasz > cbScriptSigLen && tmpl->cbtxn->data[cbScriptSigLen] + sizeof(*out_dataid) < libblkmaker_coinbase_size_minimum) {
+		// Add some padding
+		const size_t padding_required = libblkmaker_coinbase_size_minimum - (tmpl->cbtxn->data[cbScriptSigLen] + sizeof(*out_dataid));
+		uint8_t padding[padding_required];
+		static const uint8_t opcode_nop = '\x61';
+		memset(padding, opcode_nop, padding_required);
+		if (padding_required != blkmk_append_coinbase_safe2(tmpl, padding, padding_required, 0, false)) {
+			return 0;
+		}
+	}
+	
 	unsigned char *cbuf = buf;
 	
 	*out_dataid = tmpl->next_dataid++;
@@ -428,6 +439,7 @@ bool blkmk_get_mdata(blktemplate_t * const tmpl, void * const buf, const size_t
 		&& tmpl->cbtxn
 		&& blkmk_build_merkle_branches(tmpl)
 		&& bufsz >= 76
+		&& (tmpl->mutations & (BMM_CBAPPEND | BMM_CBSET))
 	))
 		return false;
 	
@@ -435,6 +447,10 @@ bool blkmk_get_mdata(blktemplate_t * const tmpl, void * const buf, const size_t
 		// Avoid overlapping with blkmk_get_data use
 		++extranoncesz;
 	
+	if (tmpl->cbtxn->datasz > cbScriptSigLen && tmpl->cbtxn->data[cbScriptSigLen] + extranoncesz < libblkmaker_coinbase_size_minimum) {
+		extranoncesz = libblkmaker_coinbase_size_minimum - tmpl->cbtxn->data[cbScriptSigLen];
+	}
+	
 	void ** const out_branches = _out_branches;
 	void ** const out_cbtxn = _out_cbtxn;
 	unsigned char *cbuf = buf;
@@ -481,9 +497,8 @@ unsigned long blkmk_work_left(const blktemplate_t *tmpl) {
 	if (!tmpl->version)
 		return 0;
 	if (!(tmpl->mutations & (BMM_CBAPPEND | BMM_CBSET)))
-		return 1;
+		return (tmpl->next_dataid) ? 0 : 1;
 	return UINT_MAX - tmpl->next_dataid;
-	return BLKMK_UNLIMITED_WORK_COUNT;
 }
 
 static
diff --git a/blkmaker_jansson.c b/blkmaker_jansson.c
index d20695a..a0ba87e 100644
--- a/blkmaker_jansson.c
+++ b/blkmaker_jansson.c
@@ -286,6 +286,8 @@ const char *blktmpl_add_jansson(blktemplate_t *tmpl, const json_t *json, time_t
 		tmpl->cbtxn = calloc(1, sizeof(*tmpl->cbtxn));
 		if ((s = parse_txn(tmpl->cbtxn, v)))
 			return s;
+	} else if (!tmpl->cbvalue) {
+		return "Missing either coinbasetxn or coinbasevalue";
 	}
 	
 	if ((v = json_object_get(json, "coinbaseaux")) && json_is_object(v))
@@ -383,7 +385,11 @@ const char *blktmpl_add_jansson(blktemplate_t *tmpl, const json_t *json, time_t
 		
 		v = json_object_get(json, "vbrequired");
 		if (v && json_is_number(v)) {
-			tmpl->vbrequired = json_number_value(v);
+			double tmpd = json_number_value(v);
+			tmpl->vbrequired = tmpd;
+			if (tmpl->vbrequired != tmpd) {
+				return "Unparsable vbrequired";
+			}
 		}
 	}
 	else
diff --git a/blktemplate.c b/blktemplate.c
index 48e2f0f..25ad0c4 100644
--- a/blktemplate.c
+++ b/blktemplate.c
@@ -26,7 +26,7 @@ static const char *capnames[] = {
 	
 	"coinbase/append",
 	"coinbase",
-	"generate",
+	"generation",
 	"time/increment",
 	"time/decrement",
 	"transactions/add",
@@ -53,6 +53,10 @@ gbt_capabilities_t blktmpl_getcapability(const char *n) {
 	for (unsigned int i = 0; i < GBT_CAPABILITY_COUNT; ++i)
 		if (capnames[i] && !strcasecmp(n, capnames[i]))
 			return 1 << i;
+	if (!strcasecmp(n, "time")) {
+		// multi-capability
+		return BMM_TIMEINC | BMM_TIMEDEC;
+	}
 	if (!strcasecmp(n, "transactions"))
 		return BMM_TXNADD;  // Odd one as it's overloaded w/"transactions/add" per spec
 	return 0;
diff --git a/blktemplate.h b/blktemplate.h
index 7772b41..b23050b 100644
--- a/blktemplate.h
+++ b/blktemplate.h
@@ -25,6 +25,7 @@ typedef int16_t blktime_diff_t;
 typedef uint32_t blknonce_t;
 
 #define libblkmaker_blkheader_size (80)
+#define libblkmaker_coinbase_size_minimum (4)
 #define libblkmaker_coinbase_size_limit (100)
 
 struct blktxn_t {
@@ -88,6 +89,7 @@ typedef enum {
 
 extern const char *blktmpl_capabilityname(gbt_capabilities_t);
 #define BLKTMPL_LONGEST_CAPABILITY_NAME  (16)
+// ABI FIXME: return uint32_t since "time" can yield a combination gbt_capabilities_t
 extern gbt_capabilities_t blktmpl_getcapability(const char *);