diff --git a/cgminer.c b/cgminer.c
index c56a77696a..104ab1a093 100644
--- a/cgminer.c
+++ b/cgminer.c
@@ -4129,7 +4129,7 @@ bool submit_work_sync(struct thr_info *thr, const struct work *work_in)
 	return false;
 }
 
-bool hashtest(const struct work *work)
+bool hashtest(const struct work *work, bool do_fulltest)
 {
 	uint32_t *data32 = (uint32_t *)(work->data);
 	unsigned char swap[128];
@@ -4150,7 +4150,10 @@ bool hashtest(const struct work *work)
 
 	memcpy((void*)work->hash, hash2, 32);
 
-	return fulltest(work->hash, work->target);
+	if (do_fulltest)
+		return fulltest(work->hash, work->target);
+	else
+		return (hash2_32[7] == 0);
 
 }
 
@@ -4168,7 +4171,7 @@ bool test_nonce(struct work *work, uint32_t nonce)
 	work->data[64 + 12 + 2] = (nonce >> 16) & 0xff;
 	work->data[64 + 12 + 3] = (nonce >> 24) & 0xff;
 
-	return hashtest(work);
+	return hashtest(work, true);
 }
 
 bool submit_nonce(struct thr_info *thr, struct work *work, uint32_t nonce)
@@ -4182,6 +4185,40 @@ bool submit_nonce(struct thr_info *thr, struct work *work, uint32_t nonce)
 	return submit_work_sync(thr, work);
 }
 
+/*
+ * Check a 1diff sha256 nonce
+ * If it doesn't hash to 1diff, then it was a HW error
+ * This is only for devices that produce 1diff sha256 nonces
+ */
+bool submit_nonce_1diff(struct thr_info *thr, struct work *work, uint32_t nonce)
+{
+	// not for scrypt - code bug
+	if (opt_scrypt) {
+		applog(LOG_ERR, "ERROR: submit_nonce_1diff() called with scrypt");
+		return true;
+	}
+
+	work->data[64 + 12 + 0] = (nonce >> 0) & 0xff;
+	work->data[64 + 12 + 1] = (nonce >> 8) & 0xff;
+	work->data[64 + 12 + 2] = (nonce >> 16) & 0xff;
+	work->data[64 + 12 + 3] = (nonce >> 24) & 0xff;
+
+	if (!hashtest(work, false)) {
+		applog(LOG_WARNING, "%s%d: invalid nonce - HW error",
+			thr->cgpu->api->name, thr->cgpu->device_id);
+		hw_errors++;
+		thr->cgpu->hw_errors++;
+		return true;
+	}
+
+	if (!fulltest(work->hash, work->target)) {
+		applog(LOG_INFO, "Share below target");
+		return true;
+	}
+
+	return submit_work_sync(thr, work);
+}
+
 static inline bool abandon_work(struct work *work, struct timeval *wdiff, uint64_t hashes)
 {
 	if (wdiff->tv_sec > opt_scantime ||
diff --git a/driver-icarus.c b/driver-icarus.c
index f1cf9d17d6..12236261c9 100644
--- a/driver-icarus.c
+++ b/driver-icarus.c
@@ -712,7 +712,7 @@ static int64_t icarus_scanhash(struct thr_info *thr, struct work *work,
 	nonce = swab32(nonce);
 #endif
 
-	submit_nonce(thr, work, nonce);
+	submit_nonce_1diff(thr, work, nonce);
 
 	hash_count = (nonce & info->nonce_mask);
 	hash_count++;
diff --git a/miner.h b/miner.h
index f87612aba5..3fa511bfec 100644
--- a/miner.h
+++ b/miner.h
@@ -824,6 +824,7 @@ struct modminer_fpga_state {
 extern void get_datestamp(char *, struct timeval *);
 extern bool test_nonce(struct work *work, uint32_t nonce);
 bool submit_nonce(struct thr_info *thr, struct work *work, uint32_t nonce);
+bool submit_nonce_1diff(struct thr_info *thr, struct work *work, uint32_t nonce);
 extern void tailsprintf(char *f, const char *fmt, ...);
 extern void wlogprint(const char *f, ...);
 extern int curses_int(const char *query);