diff --git a/novaclient/tests/unit/v2/test_shell.py b/novaclient/tests/unit/v2/test_shell.py
index e1166450b..830ce53d7 100644
--- a/novaclient/tests/unit/v2/test_shell.py
+++ b/novaclient/tests/unit/v2/test_shell.py
@@ -1773,8 +1773,11 @@ class ShellTest(utils.TestCase):
                                     'no_such_file')
         cmd = ('rebuild sample-server %s --user-data %s'
                % (FAKE_UUID_1, invalid_file))
-        self.assertRaises(exceptions.CommandError, self.run_command, cmd,
-                          api_version='2.57')
+        ex = self.assertRaises(exceptions.CommandError, self.run_command, cmd,
+                               api_version='2.57')
+        self.assertIn("Can't open '%(user_data)s': "
+                      "[Errno 2] No such file or directory: '%(user_data)s'" %
+                      {'user_data': invalid_file}, six.text_type(ex))
 
     def test_rebuild_unset_user_data(self):
         self.run_command('rebuild sample-server %s --user-data-unset' %
diff --git a/novaclient/v2/shell.py b/novaclient/v2/shell.py
index 8a1b9a6d4..ae7344bf7 100644
--- a/novaclient/v2/shell.py
+++ b/novaclient/v2/shell.py
@@ -398,7 +398,8 @@ def _boot(cs, args):
         for f in args.files:
             try:
                 dst, src = f.split('=', 1)
-                files[dst] = open(src)
+                with open(src) as fo:
+                    files[dst] = fo.read()
             except IOError as e:
                 raise exceptions.CommandError(
                     _("Can't open '%(src)s': %(exc)s") %
@@ -416,7 +417,8 @@ def _boot(cs, args):
 
     if args.user_data:
         try:
-            userdata = open(args.user_data)
+            with open(args.user_data) as f:
+                userdata = f.read()
         except IOError as e:
             raise exceptions.CommandError(_("Can't open '%(user_data)s': "
                                             "%(exc)s") %
@@ -1916,7 +1918,8 @@ def do_rebuild(cs, args):
                       "'--user-data'."))
         elif args.user_data:
             try:
-                kwargs['userdata'] = open(args.user_data)
+                with open(args.user_data) as f:
+                    kwargs['userdata'] = f.read()
             except IOError as e:
                 raise exceptions.CommandError(
                     _("Can't open '%(user_data)s': %(exc)s") % {
diff --git a/releasenotes/notes/fix-rebuild-userdata-9315e5784feb8ba9.yaml b/releasenotes/notes/fix-rebuild-userdata-9315e5784feb8ba9.yaml
index 4d5407584..32065a113 100644
--- a/releasenotes/notes/fix-rebuild-userdata-9315e5784feb8ba9.yaml
+++ b/releasenotes/notes/fix-rebuild-userdata-9315e5784feb8ba9.yaml
@@ -1,5 +1,6 @@
 ---
 fixes:
   - |
-    The user data argument to rebuild was passing the filename as is as userdata.
-    Now this passes the contents of the filename as intended.
+    The user data argument in the ``nova rebuild`` command was passing
+    the filename as userdata. Now this passes the contents of the file
+    as intended.