diff --git a/diskimage_builder/elements/growvols/static/usr/local/sbin/growvols b/diskimage_builder/elements/growvols/static/usr/local/sbin/growvols
index 8c0249e1e..0e5d4686d 100755
--- a/diskimage_builder/elements/growvols/static/usr/local/sbin/growvols
+++ b/diskimage_builder/elements/growvols/static/usr/local/sbin/growvols
@@ -36,12 +36,22 @@ UNITS = ['%']
 UNITS.extend(UNIT_BYTES.keys())
 AMOUNT_UNIT_RE = re.compile('^([0-9]+)(%s)$' % '|'.join(UNITS))
 
+UNIT_BYTES_FORMAT = {
+    'B': 1,
+    'KiB': 1024,
+    'MiB': 1048576,
+    'GiB': 1073741824
+}
+
 # Only create growth partition if there is at least 1GiB available
 MIN_DISK_SPACE_BYTES = UNIT_BYTES['GiB']
 
 # Default LVM physical extent size is 4MiB
 PHYSICAL_EXTENT_BYTES = 4 * UNIT_BYTES['MiB']
 
+# Grow the thin pool metadata size to 1GiB
+POOL_METADATA_SIZE = UNIT_BYTES['GiB']
+
 
 class Command(object):
     """ An object to represent a command to run with associated comment """
@@ -172,13 +182,13 @@ def printable_cmd(cmd):
 
 
 def convert_bytes(num):
-    """Format a bytes amount with units MB, GB etc"""
-    step_unit = 1000.0
-
-    for x in ['B', 'KB', 'MB', 'GB', 'TB']:
-        if num < step_unit:
-            return "%d%s" % (num, x)
-        num /= step_unit
+    """Format a bytes amount with units GiB, MiB etc"""
+    for x in ['GiB', 'MiB', 'KiB', 'B']:
+        unit = UNIT_BYTES_FORMAT[x]
+        unit_num = num // unit
+        if unit_num > 0:
+            break
+    return "%d%s" % (unit_num, x)
 
 
 def execute(cmd):
@@ -499,9 +509,14 @@ def main(argv):
     group = find_group(opts)
     partnum = find_next_partnum(devices, disk_name)
     devname = find_next_device_name(devices, disk_name, partnum)
+    thin_pool = find_thin_pool(devices, group)
+    if thin_pool:
+        # total size available, reduced by POOL_METADATA_SIZE
+        # rounded down to whole extent
+        size_bytes -= POOL_METADATA_SIZE
+        size_bytes -= size_bytes % PHYSICAL_EXTENT_BYTES
     dev_path = '/dev/%s' % devname
     grow_vols = find_grow_vols(opts, devices, group, size_bytes)
-    thin_pool = find_thin_pool(devices, group)
 
     commands = []
 
@@ -528,14 +543,20 @@ def main(argv):
     ], 'Add physical volume %s to group %s' % (devname, group)))
 
     if thin_pool:
-        # total size available, rounded down to whole extents
-        pool_size = size_bytes - size_bytes % PHYSICAL_EXTENT_BYTES
         commands.append(Command([
             'lvextend',
-            '-L+%sB' % pool_size,
+            '--poolmetadatasize',
+            '+%sB' % POOL_METADATA_SIZE,
             thin_pool,
             dev_path
-        ], 'Add %s to thin pool %s' % (convert_bytes(pool_size),
+        ], 'Add %s to thin pool metadata %s' % (
+            convert_bytes(POOL_METADATA_SIZE), thin_pool)))
+        commands.append(Command([
+            'lvextend',
+            '-L+%sB' % size_bytes,
+            thin_pool,
+            dev_path
+        ], 'Add %s to thin pool %s' % (convert_bytes(size_bytes),
                                                      thin_pool)))
 
     for volume_path, size_bytes in grow_vols.items():
diff --git a/diskimage_builder/elements/growvols/tests/test_growvols.py b/diskimage_builder/elements/growvols/tests/test_growvols.py
index 7c2deb910..db1f87c7d 100644
--- a/diskimage_builder/elements/growvols/tests/test_growvols.py
+++ b/diskimage_builder/elements/growvols/tests/test_growvols.py
@@ -147,10 +147,10 @@ class TestGrowvols(base.BaseTestCase):
 
     def test_convert_bytes(self):
         self.assertEqual('100B', growvols.convert_bytes(100))
-        self.assertEqual('1KB', growvols.convert_bytes(1000))
-        self.assertEqual('2MB', growvols.convert_bytes(2000000))
-        self.assertEqual('3GB', growvols.convert_bytes(3000000000))
-        self.assertEqual('4TB', growvols.convert_bytes(4000000000000))
+        self.assertEqual('1000B', growvols.convert_bytes(1000))
+        self.assertEqual('1MiB', growvols.convert_bytes(2000000))
+        self.assertEqual('2GiB', growvols.convert_bytes(3000000000))
+        self.assertEqual('3725GiB', growvols.convert_bytes(4000000000000))
 
     @mock.patch('subprocess.Popen')
     def test_execute(self, mock_popen):
@@ -582,7 +582,7 @@ class TestGrowvols(base.BaseTestCase):
             SGDISK_LARGEST,
             VGS,
             LVS_THIN,
-            '', '', '', '', '', '', '', '', '', '', ''
+            '', '', '', '', '', '', '', '', '', '', '', ''
         ]
         growvols.main(['growvols', '--yes', '--group', 'vg',
                        '/home=20%', 'fs_var=40%'])
@@ -599,13 +599,15 @@ class TestGrowvols(base.BaseTestCase):
             mock.call(['partprobe']),
             mock.call(['pvcreate', '/dev/sda5']),
             mock.call(['vgextend', 'vg', '/dev/sda5']),
-            mock.call(['lvextend', '-L+209404821504B',
+            mock.call(['lvextend', '--poolmetadatasize', '+1073741824B',
                        '/dev/mapper/vg-lv_thinpool', '/dev/sda5']),
-            mock.call(['lvextend', '--size', '+41880125440B',
+            mock.call(['lvextend', '-L+208331079680B',
+                       '/dev/mapper/vg-lv_thinpool', '/dev/sda5']),
+            mock.call(['lvextend', '--size', '+41666215936B',
                        '/dev/mapper/vg-lv_home']),
-            mock.call(['lvextend', '--size', '+83760250880B',
+            mock.call(['lvextend', '--size', '+83332431872B',
                        '/dev/mapper/vg-lv_var']),
-            mock.call(['lvextend', '--size', '+83764445184B',
+            mock.call(['lvextend', '--size', '+83332431872B',
                        '/dev/mapper/vg-lv_root']),
             mock.call(['xfs_growfs', '/dev/mapper/vg-lv_home']),
             mock.call(['xfs_growfs', '/dev/mapper/vg-lv_var']),