diff --git a/test-tool/test_writesame10_unmap.c b/test-tool/test_writesame10_unmap.c
index 07d7870..065efff 100644
--- a/test-tool/test_writesame10_unmap.c
+++ b/test-tool/test_writesame10_unmap.c
@@ -26,11 +26,28 @@
 #include "iscsi-test-cu.h"
 
 
+static const unsigned char zeroBlock[4096];
+
+static int all_zeroes(const unsigned char *buf, unsigned size)
+{
+	unsigned j, e;
+
+	for (j = 0; j < size; j += sizeof(zeroBlock)) {
+		e = size - j;
+		if (sizeof(zeroBlock) < e)
+			e = sizeof(zeroBlock);
+		if (memcmp(buf + j, zeroBlock, e) != 0)
+			return 0;
+	}
+
+	return 1;
+}
+
 void
 test_writesame10_unmap(void)
 {
 	int ret;
-	unsigned int i, j;
+	unsigned int i;
 	unsigned char *buf = alloca(256 * block_size);
 
 	CHECK_FOR_DATALOSS;
@@ -66,11 +83,7 @@ test_writesame10_unmap(void)
 				     i * block_size, block_size,
 				     0, 0, 0, 0, 0, buf,
 				     EXPECT_STATUS_GOOD);
-			for (j = 0; j < block_size * i; j++) {
-				if (buf[j] != 0) {
-					CU_ASSERT_EQUAL(buf[j], 0);
-				}
-			}
+			CU_ASSERT(all_zeroes(buf, i * block_size));
 		} else {
 			logging(LOG_VERBOSE, "LBPRZ is clear. Skip the read "
 				"and verify zero test");
@@ -105,11 +118,7 @@ test_writesame10_unmap(void)
 				     i * block_size, block_size,
 				     0, 0, 0, 0, 0, buf,
 				     EXPECT_STATUS_GOOD);
-			for (j = 0; j < block_size * i; j++) {
-				if (buf[j] != 0) {
-					CU_ASSERT_EQUAL(buf[j], 0);
-				}
-			}
+			CU_ASSERT(all_zeroes(buf, i * block_size));
 		} else {
 			logging(LOG_VERBOSE, "LBPRZ is clear. Skip the read "
 				"and verify zero test");
@@ -181,11 +190,7 @@ test_writesame10_unmap(void)
 				     i * block_size, block_size,
 				     0, 0, 0, 0, 0, buf,
 				     EXPECT_STATUS_GOOD);
-			for (j = 0; j < block_size * i; j++) {
-				if (buf[j] != 0) {
-					CU_ASSERT_EQUAL(buf[j], 0);
-				}
-			}
+			CU_ASSERT(all_zeroes(buf, i * block_size));
 		} else {
 			logging(LOG_VERBOSE, "LBPRZ is clear. Skip the read "
 				"and verify zero test");
diff --git a/test-tool/test_writesame16_unmap.c b/test-tool/test_writesame16_unmap.c
index 04280c8..0a019f4 100644
--- a/test-tool/test_writesame16_unmap.c
+++ b/test-tool/test_writesame16_unmap.c
@@ -25,13 +25,29 @@
 #include "iscsi-test-cu.h"
 
 
+static const unsigned char zeroBlock[4096];
+
+static int all_zeroes(const unsigned char *buf, unsigned size)
+{
+	unsigned j, e;
+
+	for (j = 0; j < size; j += sizeof(zeroBlock)) {
+		e = size - j;
+		if (sizeof(zeroBlock) < e)
+			e = sizeof(zeroBlock);
+		if (memcmp(buf + j, zeroBlock, e) != 0)
+			return 0;
+	}
+
+	return 1;
+}
+
 void
 test_writesame16_unmap(void)
 {
 	int ret;
-	unsigned int i, j;
+	unsigned int i;
 	unsigned char *buf;
-	unsigned char *zeroBlock;
 
 	CHECK_FOR_DATALOSS;
 	CHECK_FOR_THIN_PROVISIONING;
@@ -41,8 +57,6 @@ test_writesame16_unmap(void)
 	logging(LOG_VERBOSE, LOG_BLANK_LINE);
 	logging(LOG_VERBOSE, "Test WRITESAME16 of 1-256 blocks at the start of the LUN");
 	buf = malloc(65536 * block_size);
-	zeroBlock = alloca(block_size);
-	memset(zeroBlock, 0, block_size);
 	for (i = 1; i <= 256; i++) {
 		logging(LOG_VERBOSE, "Write %d blocks of 0xFF", i);
 		memset(buf, 0xff, i * block_size);
@@ -70,9 +84,7 @@ test_writesame16_unmap(void)
 				     i * block_size, block_size,
 				     0, 0, 0, 0, 0, buf,
 				     EXPECT_STATUS_GOOD);
-			for (j = 0; j < i; j++) {
-				CU_ASSERT_EQUAL(memcmp(buf + j*block_size, zeroBlock, block_size), 0);
-			}
+			CU_ASSERT(all_zeroes(buf, i * block_size));
 		} else {
 			logging(LOG_VERBOSE, "LBPRZ is clear. Skip the read "
 				"and verify zero test");
@@ -105,9 +117,7 @@ test_writesame16_unmap(void)
 				     i * block_size, block_size,
 				     0, 0, 0, 0, 0, buf,
 				     EXPECT_STATUS_GOOD);
-			for (j = 0; j < i; j++) {
-				CU_ASSERT_EQUAL(memcmp(buf + j*block_size, zeroBlock, block_size), 0);
-			}
+			CU_ASSERT(all_zeroes(buf, i * block_size));
 		} else {
 			logging(LOG_VERBOSE, "LBPRZ is clear. Skip the read "
 				"and verify zero test");
@@ -178,9 +188,7 @@ test_writesame16_unmap(void)
 				     i * block_size, block_size,
 				     0, 0, 0, 0, 0, buf,
 				     EXPECT_STATUS_GOOD);
-			for (j = 0; j < i; j++) {
-				CU_ASSERT_EQUAL(memcmp(buf + j*block_size, zeroBlock, block_size), 0);
-			}
+			CU_ASSERT(all_zeroes(buf, i * block_size));
 		} else {
 			logging(LOG_VERBOSE, "LBPRZ is clear. Skip the read "
 				"and verify zero test");
@@ -230,9 +238,7 @@ test_writesame16_unmap(void)
 				     i * block_size, block_size,
 				     0, 0, 0, 0, 0, buf,
 				     EXPECT_STATUS_GOOD);
-			for (j = 0; j < i; j++) {
-				CU_ASSERT_EQUAL(memcmp(buf + j*block_size, zeroBlock, block_size), 0);
-			}
+			CU_ASSERT(all_zeroes(buf, i * block_size));
 		} else {
 			logging(LOG_VERBOSE, "LBPRZ is clear. Skip the read "
 				"and verify zero test");