diff --git a/Makefile.am b/Makefile.am
index 7a1ca9b..a5f0489 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -200,6 +200,7 @@ bin_iscsi_test_cu_SOURCES = test-tool/iscsi-test-cu.c \
 	test-tool/test_readcapacity16_simple.c \
 	test-tool/test_readcapacity16_alloclen.c \
 	test-tool/test_unmap_simple.c \
+	test-tool/test_unmap_0blocks.c \
 	test-tool/test_verify10_simple.c \
 	test-tool/test_verify10_beyond_eol.c \
 	test-tool/test_verify10_0blocks.c \
diff --git a/test-tool/iscsi-test-cu.c b/test-tool/iscsi-test-cu.c
index d05916a..4b07998 100644
--- a/test-tool/iscsi-test-cu.c
+++ b/test-tool/iscsi-test-cu.c
@@ -110,6 +110,7 @@ static CU_TestInfo tests_readcapacity16[] = {
 
 static CU_TestInfo tests_unmap[] = {
 	{ (char *)"testUnmapSimple", test_unmap_simple },
+	{ (char *)"testUnmapZeroBlocks", test_unmap_0blocks },
 	CU_TEST_INFO_NULL
 };
 
@@ -518,7 +519,7 @@ main(int argc, char *argv[])
 		return -1;
 	}
 	block_size = rc10->block_size;
-	num_blocks = rc10->lba;
+	num_blocks = rc10->lba + 1;
 	scsi_free_scsi_task(task);
 
 	task = iscsi_readcapacity16_sync(iscsic, lun);
@@ -538,7 +539,7 @@ main(int argc, char *argv[])
 			return -1;
 		}
 		block_size = rc16->block_length;
-		num_blocks = rc16->returned_lba;
+		num_blocks = rc16->returned_lba + 1;
 		lbpme = rc16->lbpme;
 		lbppb = 1 << rc16->lbppbe;
 		lbpme = rc16->lbpme;
diff --git a/test-tool/iscsi-test-cu.h b/test-tool/iscsi-test-cu.h
index 3e4b302..de205e7 100644
--- a/test-tool/iscsi-test-cu.h
+++ b/test-tool/iscsi-test-cu.h
@@ -68,6 +68,7 @@ void test_readcapacity16_simple(void);
 void test_readcapacity16_alloclen(void);
 
 void test_unmap_simple(void);
+void test_unmap_0blocks(void);
 
 void test_verify10_simple(void);
 void test_verify10_beyond_eol(void);
diff --git a/test-tool/test_read10_simple.c b/test-tool/test_read10_simple.c
index 0005ee0..91bf8dc 100644
--- a/test-tool/test_read10_simple.c
+++ b/test-tool/test_read10_simple.c
@@ -43,7 +43,7 @@ test_read10_simple(void)
 
 	logging(LOG_VERBOSE, "Test READ10 of 1-256 blocks at the end of the LUN");
 	for (i = 1; i <= 256; i++) {
-		ret = read10(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read10(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 0, 0, 0, NULL);
 		CU_ASSERT_EQUAL(ret, 0);
 	}
diff --git a/test-tool/test_read12_simple.c b/test-tool/test_read12_simple.c
index 2147589..a55d50c 100644
--- a/test-tool/test_read12_simple.c
+++ b/test-tool/test_read12_simple.c
@@ -43,7 +43,7 @@ test_read12_simple(void)
 
 	logging(LOG_VERBOSE, "Test READ12 of 1-256 blocks at the end of the LUN");
 	for (i = 1; i <= 256; i++) {
-		ret = read12(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read12(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 0, 0, 0, NULL);
 		CU_ASSERT_EQUAL(ret, 0);
 	}
diff --git a/test-tool/test_read16_simple.c b/test-tool/test_read16_simple.c
index 9bfc4e4..5781b07 100644
--- a/test-tool/test_read16_simple.c
+++ b/test-tool/test_read16_simple.c
@@ -44,7 +44,7 @@ test_read16_simple(void)
 
 	logging(LOG_VERBOSE, "Test READ16 of 1-256 blocks at the end of the LUN");
 	for (i = 1; i <= 256; i++) {
-		ret = read16(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read16(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 0, 0, 0, NULL);
 		CU_ASSERT_EQUAL(ret, 0);
 	}
diff --git a/test-tool/test_read6_simple.c b/test-tool/test_read6_simple.c
index 5110d2c..1cffc3b 100644
--- a/test-tool/test_read6_simple.c
+++ b/test-tool/test_read6_simple.c
@@ -43,7 +43,7 @@ test_read6_simple(void)
 
 	logging(LOG_VERBOSE, "Test READ6 of 1-255 blocks at the end of the LUN");
 	for (i = 1; i <= 255; i++) {
-		ret = read6(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read6(iscsic, tgt_lun, num_blocks - i,
 			    i * block_size, block_size, NULL);
 		CU_ASSERT_EQUAL(ret, 0);
 	}
diff --git a/test-tool/test_unmap_0blocks.c b/test-tool/test_unmap_0blocks.c
new file mode 100644
index 0000000..75921c5
--- /dev/null
+++ b/test-tool/test_unmap_0blocks.c
@@ -0,0 +1,61 @@
+
+/* 
+   Copyright (C) 2013 Ronnie Sahlberg <ronniesahlberg@gmail.com>
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <stdio.h>
+
+#include <CUnit/CUnit.h>
+
+#include "iscsi.h"
+#include "scsi-lowlevel.h"
+#include "iscsi-support.h"
+#include "iscsi-test-cu.h"
+
+
+void
+test_unmap_0blocks(void)
+{
+	int i, ret;
+	struct unmap_list list[257];
+
+	CHECK_FOR_DATALOSS;
+	CHECK_FOR_THIN_PROVISIONING;
+	CHECK_FOR_SBC;
+
+	logging(LOG_VERBOSE, "");
+	logging(LOG_VERBOSE, "Test UNMAP of 0 blocks at LBA:0-255 as a single descriptor");
+	for (i = 0; i < 256; i++) {
+		list[0].lba = i;
+		list[0].num = 0;
+		ret = unmap(iscsic, tgt_lun, 0, list, 1);
+		CU_ASSERT_EQUAL(ret, 0);
+	}
+
+	logging(LOG_VERBOSE, "Test UNMAP of 0 blocks at LBA:0-255  with one descriptor per block");
+	for (i = 0; i < 256; i++) {
+		list[i].lba = i;
+		list[i].num = 0;
+		ret = unmap(iscsic, tgt_lun, 0, list, i);
+		CU_ASSERT_EQUAL(ret, 0);
+	}
+
+	logging(LOG_VERBOSE, "Test UNMAP of 0 blocks at end-of-LUN");
+	list[0].lba = num_blocks;
+	list[0].num = 0;
+	ret = unmap(iscsic, tgt_lun, 0, list, 1);
+	CU_ASSERT_EQUAL(ret, 0);
+}
diff --git a/test-tool/test_unmap_simple.c b/test-tool/test_unmap_simple.c
index aeb7bf7..9b8b297 100644
--- a/test-tool/test_unmap_simple.c
+++ b/test-tool/test_unmap_simple.c
@@ -47,10 +47,10 @@ test_unmap_simple(void)
 
 
 	logging(LOG_VERBOSE, "Test UNMAP of 1-256 blocks at the start of the LUN with one descriptor per block");
-	for (i = 1; i <= 256; i++) {
-		list[i].lba = i-1;
+	for (i = 0; i < 256; i++) {
+		list[i].lba = i;
 		list[i].num = 1;
-		ret = unmap(iscsic, tgt_lun, 0, list, i);
+		ret = unmap(iscsic, tgt_lun, 0, list, i + 1);
 		CU_ASSERT_EQUAL(ret, 0);
 	}
 }
diff --git a/test-tool/test_verify10_mismatch.c b/test-tool/test_verify10_mismatch.c
index 9710d3d..de4828f 100644
--- a/test-tool/test_verify10_mismatch.c
+++ b/test-tool/test_verify10_mismatch.c
@@ -60,7 +60,7 @@ test_verify10_mismatch(void)
 		unsigned char *buf = malloc(block_size * i);
 		int offset = random() % (i * block_size);
 
-		ret = read10(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read10(iscsic, tgt_lun, num_blocks - i,
 			     i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		CU_ASSERT_EQUAL(ret, 0);
 
@@ -68,7 +68,7 @@ test_verify10_mismatch(void)
 		buf[offset] ^= 'X';
 		logging(LOG_VERBOSE, "Flip some bits in the data");
 
-		ret = verify10_miscompare(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = verify10_miscompare(iscsic, tgt_lun, num_blocks - i,
 					  i * block_size, block_size, 0, 0, 1, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_verify10_mismatch_no_cmp.c b/test-tool/test_verify10_mismatch_no_cmp.c
index 6411dcd..6bb0ad9 100644
--- a/test-tool/test_verify10_mismatch_no_cmp.c
+++ b/test-tool/test_verify10_mismatch_no_cmp.c
@@ -61,7 +61,7 @@ test_verify10_mismatch_no_cmp(void)
 		unsigned char *buf = malloc(block_size * i);
 		int offset = random() % (i * block_size);
 
-		ret = read10(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read10(iscsic, tgt_lun, num_blocks - i,
 			     i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		CU_ASSERT_EQUAL(ret, 0);
 
@@ -69,7 +69,7 @@ test_verify10_mismatch_no_cmp(void)
 		buf[offset] ^= 'X';
 		logging(LOG_VERBOSE, "Flip some bits in the data");
 
-		ret = verify10(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = verify10(iscsic, tgt_lun, num_blocks - i,
 			       i * block_size, block_size, 0, 0, 0, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_verify10_simple.c b/test-tool/test_verify10_simple.c
index b51df7c..654a918 100644
--- a/test-tool/test_verify10_simple.c
+++ b/test-tool/test_verify10_simple.c
@@ -54,11 +54,11 @@ test_verify10_simple(void)
 	for (i = 1; i <= 256; i++) {
 		unsigned char *buf = malloc(block_size * i);
 
-		ret = read10(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read10(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		CU_ASSERT_EQUAL(ret, 0);
 
-		ret = verify10(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = verify10(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 1, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_verify12_mismatch.c b/test-tool/test_verify12_mismatch.c
index c2c3dc9..4d76845 100644
--- a/test-tool/test_verify12_mismatch.c
+++ b/test-tool/test_verify12_mismatch.c
@@ -60,7 +60,7 @@ test_verify12_mismatch(void)
 		unsigned char *buf = malloc(block_size * i);
 		int offset = random() % (i * block_size);
 
-		ret = read12(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read12(iscsic, tgt_lun, num_blocks - i,
 			     i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		CU_ASSERT_EQUAL(ret, 0);
 
@@ -68,7 +68,7 @@ test_verify12_mismatch(void)
 		buf[offset] ^= 'X';
 		logging(LOG_VERBOSE, "Flip some bits in the data");
 
-		ret = verify12_miscompare(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = verify12_miscompare(iscsic, tgt_lun, num_blocks - i,
 					  i * block_size, block_size, 0, 0, 1, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_verify12_mismatch_no_cmp.c b/test-tool/test_verify12_mismatch_no_cmp.c
index dc9783c..8c72c0e 100644
--- a/test-tool/test_verify12_mismatch_no_cmp.c
+++ b/test-tool/test_verify12_mismatch_no_cmp.c
@@ -61,7 +61,7 @@ test_verify12_mismatch_no_cmp(void)
 		unsigned char *buf = malloc(block_size * i);
 		int offset = random() % (i * block_size);
 
-		ret = read12(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read12(iscsic, tgt_lun, num_blocks - i,
 			     i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		CU_ASSERT_EQUAL(ret, 0);
 
@@ -69,7 +69,7 @@ test_verify12_mismatch_no_cmp(void)
 		buf[offset] ^= 'X';
 		logging(LOG_VERBOSE, "Flip some bits in the data");
 
-		ret = verify12(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = verify12(iscsic, tgt_lun, num_blocks - i,
 			       i * block_size, block_size, 0, 0, 0, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_verify12_simple.c b/test-tool/test_verify12_simple.c
index 02f7ec4..a3c25f7 100644
--- a/test-tool/test_verify12_simple.c
+++ b/test-tool/test_verify12_simple.c
@@ -54,11 +54,11 @@ test_verify12_simple(void)
 	for (i = 1; i <= 256; i++) {
 		unsigned char *buf = malloc(block_size * i);
 
-		ret = read12(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read12(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		CU_ASSERT_EQUAL(ret, 0);
 
-		ret = verify12(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = verify12(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 1, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_verify16_mismatch.c b/test-tool/test_verify16_mismatch.c
index 33f7657..7a0c4d8 100644
--- a/test-tool/test_verify16_mismatch.c
+++ b/test-tool/test_verify16_mismatch.c
@@ -60,7 +60,7 @@ test_verify16_mismatch(void)
 		unsigned char *buf = malloc(block_size * i);
 		int offset = random() % (i * block_size);
 
-		ret = read16(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read16(iscsic, tgt_lun, num_blocks - i,
 			     i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		CU_ASSERT_EQUAL(ret, 0);
 
@@ -68,7 +68,7 @@ test_verify16_mismatch(void)
 		buf[offset] ^= 'X';
 		logging(LOG_VERBOSE, "Flip some bits in the data");
 
-		ret = verify16_miscompare(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = verify16_miscompare(iscsic, tgt_lun, num_blocks - i,
 					  i * block_size, block_size, 0, 0, 1, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_verify16_mismatch_no_cmp.c b/test-tool/test_verify16_mismatch_no_cmp.c
index 63a2ed9..ef00b57 100644
--- a/test-tool/test_verify16_mismatch_no_cmp.c
+++ b/test-tool/test_verify16_mismatch_no_cmp.c
@@ -61,7 +61,7 @@ test_verify16_mismatch_no_cmp(void)
 		unsigned char *buf = malloc(block_size * i);
 		int offset = random() % (i * block_size);
 
-		ret = read16(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read16(iscsic, tgt_lun, num_blocks - i,
 			     i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		CU_ASSERT_EQUAL(ret, 0);
 
@@ -69,7 +69,7 @@ test_verify16_mismatch_no_cmp(void)
 		buf[offset] ^= 'X';
 		logging(LOG_VERBOSE, "Flip some bits in the data");
 
-		ret = verify16(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = verify16(iscsic, tgt_lun, num_blocks - i,
 			       i * block_size, block_size, 0, 0, 0, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_verify16_simple.c b/test-tool/test_verify16_simple.c
index 609fa38..671eaea 100644
--- a/test-tool/test_verify16_simple.c
+++ b/test-tool/test_verify16_simple.c
@@ -54,11 +54,11 @@ test_verify16_simple(void)
 	for (i = 1; i <= 256; i++) {
 		unsigned char *buf = malloc(block_size * i);
 
-		ret = read16(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = read16(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		CU_ASSERT_EQUAL(ret, 0);
 
-		ret = verify16(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = verify16(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 1, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_write10_simple.c b/test-tool/test_write10_simple.c
index 0ba8c13..bb45b88 100644
--- a/test-tool/test_write10_simple.c
+++ b/test-tool/test_write10_simple.c
@@ -49,7 +49,7 @@ test_write10_simple(void)
 	for (i = 1; i <= 256; i++) {
 		unsigned char *buf = malloc(block_size * i);
 
-		ret = write10(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = write10(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_write12_simple.c b/test-tool/test_write12_simple.c
index 48e295f..36eec57 100644
--- a/test-tool/test_write12_simple.c
+++ b/test-tool/test_write12_simple.c
@@ -49,7 +49,7 @@ test_write12_simple(void)
 	for (i = 1; i <= 256; i++) {
 		unsigned char *buf = malloc(block_size * i);
 
-		ret = write12(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = write12(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);
diff --git a/test-tool/test_write16_simple.c b/test-tool/test_write16_simple.c
index 7b9587b..4dea767 100644
--- a/test-tool/test_write16_simple.c
+++ b/test-tool/test_write16_simple.c
@@ -50,7 +50,7 @@ test_write16_simple(void)
 	for (i = 1; i <= 256; i++) {
 		unsigned char *buf = malloc(block_size * i);
 
-		ret = write16(iscsic, tgt_lun, num_blocks +1 - i,
+		ret = write16(iscsic, tgt_lun, num_blocks - i,
 		    i * block_size, block_size, 0, 0, 0, 0, 0, buf);
 		free(buf);
 		CU_ASSERT_EQUAL(ret, 0);