diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
index 9e023a4..df7297f 100644
--- a/qemu-io-cmds.c
+++ b/qemu-io-cmds.c
@@ -1760,7 +1760,7 @@ out:
 static int alloc_f(BlockBackend *blk, int argc, char **argv)
 {
     BlockDriverState *bs = blk_bs(blk);
-    int64_t offset, sector_num, nb_sectors, remaining;
+    int64_t offset, sector_num, nb_sectors, remaining, bytes;
     char s1[64];
     int num, ret;
     int64_t sum_alloc;
@@ -1776,18 +1776,24 @@ static int alloc_f(BlockBackend *blk, int argc, char **argv)
     }

     if (argc == 3) {
-        nb_sectors = cvtnum(argv[2]);
-        if (nb_sectors < 0) {
-            print_cvtnum_err(nb_sectors, argv[2]);
+        bytes = cvtnum(argv[2]);
+        if (bytes < 0) {
+            print_cvtnum_err(bytes, argv[2]);
             return 0;
-        } else if (nb_sectors > INT_MAX) {
-            printf("length argument cannot exceed %d, given %s\n",
-                   INT_MAX, argv[2]);
+        } else if (bytes > INT_MAX * BDRV_SECTOR_SIZE) {
+            printf("length argument cannot exceed %llu, given %s\n",
+                   INT_MAX * BDRV_SECTOR_SIZE, argv[2]);
             return 0;
         }
     } else {
-        nb_sectors = 1;
+        bytes = BDRV_SECTOR_SIZE;
     }
+    if (bytes & 0x1ff) {
+        printf("bytes %" PRId64 " is not sector aligned\n",
+               bytes);
+        return 0;
+    }
+    nb_sectors = bytes >> BDRV_SECTOR_BITS;

     remaining = nb_sectors;
     sum_alloc = 0;
@@ -1811,8 +1817,8 @@ static int alloc_f(BlockBackend *blk, int argc, char **argv)

     cvtstr(offset, s1, sizeof(s1));

-    printf("%"PRId64"/%"PRId64" sectors allocated at offset %s\n",
-           sum_alloc, nb_sectors, s1);
+    printf("%"PRId64"/%"PRId64" bytes allocated at offset %s\n",
+           sum_alloc << BDRV_SECTOR_BITS, nb_sectors << BDRV_SECTOR_BITS, s1);
     return 0;
 }

@@ -1822,8 +1828,8 @@ static const cmdinfo_t alloc_cmd = {
     .argmin     = 1,
     .argmax     = 2,
     .cfunc      = alloc_f,
-    .args       = "off [sectors]",
-    .oneline    = "checks if a sector is present in the file",
+    .args       = "offset [bytes]",
+    .oneline    = "checks if offset is allocated in the file",
 };


diff --git a/tests/qemu-iotests/019.out b/tests/qemu-iotests/019.out
index 0124264..17a7c03 100644
--- a/tests/qemu-iotests/019.out
+++ b/tests/qemu-iotests/019.out
@@ -542,8 +542,8 @@ Testing conversion with -B TEST_DIR/t.IMGFMT.base

 Checking if backing clusters are allocated when they shouldn't

-0/128 sectors allocated at offset 1 MiB
-0/128 sectors allocated at offset 4.001 GiB
+0/65536 bytes allocated at offset 1 MiB
+0/65536 bytes allocated at offset 4.001 GiB
 Reading

 === IO: pattern 42
@@ -1086,8 +1086,8 @@ Testing conversion with -o backing_file=TEST_DIR/t.IMGFMT.base

 Checking if backing clusters are allocated when they shouldn't

-0/128 sectors allocated at offset 1 MiB
-0/128 sectors allocated at offset 4.001 GiB
+0/65536 bytes allocated at offset 1 MiB
+0/65536 bytes allocated at offset 4.001 GiB
 Reading

 === IO: pattern 42
diff --git a/tests/qemu-iotests/179 b/tests/qemu-iotests/179
index 338a45d..44541e1 100755
--- a/tests/qemu-iotests/179
+++ b/tests/qemu-iotests/179
@@ -62,12 +62,12 @@ $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
 # But not requesting unmap must result in allocation (whether a cluster
 # allocation in compat=0.10 or a flag allocation in compat=1.1).
 $QEMU_IO -c "write -z 5M 1M" "$TEST_IMG.base" | _filter_qemu_io
-$QEMU_IO -c "alloc 5M $((1024*1024 / 512))" "$TEST_IMG.base" | _filter_qemu_io
+$QEMU_IO -c "alloc 5M 1M" "$TEST_IMG.base" | _filter_qemu_io

 # Presence of a backing file overrides permission to unmap.  Again,
 # compat=0.10 images allocate, while compat=1.1 images set zero flag.
 $QEMU_IO -c "write -z -u 7M 1M" "$TEST_IMG" | _filter_qemu_io
-$QEMU_IO -c "alloc 7M $((1024 * 1024 / 512))" "$TEST_IMG" | _filter_qemu_io
+$QEMU_IO -c "alloc 7M 1M" "$TEST_IMG" | _filter_qemu_io

 # Final check that images are still sane.
 TEST_IMG="$TEST_IMG.base" _check_test_img
diff --git a/tests/qemu-iotests/179.out b/tests/qemu-iotests/179.out
index fc97b19..18ecf0f 100644
--- a/tests/qemu-iotests/179.out
+++ b/tests/qemu-iotests/179.out
@@ -13,10 +13,10 @@ wrote 1048576/1048576 bytes at offset 3145728
 [{ "start": 0, "length": 16777216, "depth": 1, "zero": true, "data": false}]
 wrote 1048576/1048576 bytes at offset 5242880
 1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-2048/2048 sectors allocated at offset 5 MiB
+1048576/1048576 bytes allocated at offset 5 MiB
 wrote 1048576/1048576 bytes at offset 7340032
 1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-2048/2048 sectors allocated at offset 7 MiB
+1048576/1048576 bytes allocated at offset 7 MiB
 No errors were found on the image.
 No errors were found on the image.
 *** done
diff --git a/tests/qemu-iotests/common.pattern b/tests/qemu-iotests/common.pattern
index ddfbca1..34f4a8d 100644
--- a/tests/qemu-iotests/common.pattern
+++ b/tests/qemu-iotests/common.pattern
@@ -18,7 +18,7 @@

 function do_is_allocated() {
     local start=$1
-    local size=$(( $2 / 512))
+    local size=$2
     local step=$3
     local count=$4

