diff --git a/ironic_inspector/plugins/standard.py b/ironic_inspector/plugins/standard.py
index a0f4143cd..4ba17b623 100644
--- a/ironic_inspector/plugins/standard.py
+++ b/ironic_inspector/plugins/standard.py
@@ -76,11 +76,17 @@ class RootDiskSelectionHook(base.ProcessingHook):
         root_disk = introspection_data.get('root_disk')
         if root_disk:
             local_gb = root_disk['size'] // units.Gi
-            if CONF.processing.disk_partitioning_spacing:
-                local_gb -= 1
-            LOG.info('Root disk %(disk)s, local_gb %(local_gb)s GiB',
-                     {'disk': root_disk, 'local_gb': local_gb},
-                     node_info=node_info, data=introspection_data)
+            if not local_gb:
+                LOG.warning('The requested root disk is too small (smaller '
+                            'than 1 GiB) or its size cannot be detected: %s',
+                            root_disk,
+                            node_info=node_info, data=introspection_data)
+            else:
+                if CONF.processing.disk_partitioning_spacing:
+                    local_gb -= 1
+                LOG.info('Root disk %(disk)s, local_gb %(local_gb)s GiB',
+                         {'disk': root_disk, 'local_gb': local_gb},
+                         node_info=node_info, data=introspection_data)
         else:
             local_gb = 0
             LOG.info('No root device found, assuming a diskless node',
diff --git a/ironic_inspector/test/unit/test_plugins_standard.py b/ironic_inspector/test/unit/test_plugins_standard.py
index c87d0bb75..1acbbbe03 100644
--- a/ironic_inspector/test/unit/test_plugins_standard.py
+++ b/ironic_inspector/test/unit/test_plugins_standard.py
@@ -363,6 +363,7 @@ class TestRootDiskSelection(test_base.NodeTest):
             {'model': 'Model 3', 'size': 10 * units.Gi, 'name': '/dev/sdc'},
             {'model': 'Model 4', 'size': 4 * units.Gi, 'name': '/dev/sdd'},
             {'model': 'Too Small', 'size': 1 * units.Gi, 'name': '/dev/sde'},
+            {'model': 'Floppy', 'size': 0, 'name': '/dev/sdf'},
         ]
         self.matched = self.inventory['disks'][2].copy()
         self.node_info = mock.Mock(spec=node_cache.NodeInfo,
@@ -434,6 +435,15 @@ class TestRootDiskSelection(test_base.NodeTest):
         self.assertEqual(10, self.data['local_gb'])
         self.node_info.update_properties.assert_called_once_with(local_gb='10')
 
+    def test_zero_size(self):
+        self.node.properties['root_device'] = {'name': '/dev/sdf'}
+
+        self.hook.before_update(self.data, self.node_info)
+
+        self.assertEqual(self.inventory['disks'][5], self.data['root_disk'])
+        self.assertEqual(0, self.data['local_gb'])
+        self.node_info.update_properties.assert_called_once_with(local_gb='0')
+
     def test_all_match(self):
         self.node.properties['root_device'] = {'size': 10,
                                                'model': 'Model 3'}
diff --git a/releasenotes/notes/zero-size-55c4b4f2b9e8384d.yaml b/releasenotes/notes/zero-size-55c4b4f2b9e8384d.yaml
new file mode 100644
index 000000000..bd48a9e16
--- /dev/null
+++ b/releasenotes/notes/zero-size-55c4b4f2b9e8384d.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    No longer tries to set ``local_gb`` to -1 if the matched root device has
+    size of zero.