diff --git a/src/pybind/mgr/orchestrator/_interface.py b/src/pybind/mgr/orchestrator/_interface.py
index 545054d3ea0..d72d8af97eb 100644
--- a/src/pybind/mgr/orchestrator/_interface.py
+++ b/src/pybind/mgr/orchestrator/_interface.py
@@ -23,7 +23,7 @@ from mgr_module import MgrModule, CLICommand, HandleCommandResult
 
 try:
     from typing import TypeVar, Generic, List, Optional, Union, Tuple, Iterator, Callable, Any, \
-        Type, Sequence, Dict
+    Type, Sequence, Dict, cast
 except ImportError:
     pass
 
@@ -223,8 +223,11 @@ class _Promise(object):
         Call ``on_complete`` as soon as this promise is finalized.
         """
         assert self._state in (self.INITIALIZED, self.RUNNING)
+
+        if self._next_promise is not None:
+            return self._next_promise.then(on_complete)
+
         if self._on_complete is not None:
-            assert self._next_promise is None
             self._set_next_promise(self.__class__(
                 _first_promise=self._first_promise,
                 on_complete=on_complete
@@ -848,25 +851,33 @@ class Orchestrator(object):
         """
         Applies any spec
         """
-        fns = {
+        fns: Dict[str, Callable[[ServiceSpec], Completion]] = {
             'alertmanager': self.apply_alertmanager,
             'crash': self.apply_crash,
             'grafana': self.apply_grafana,
             'mds': self.apply_mds,
             'mgr': self.apply_mgr,
             'mon': self.apply_mon,
-            'nfs': self.apply_nfs,
+            'nfs': cast(Callable[[ServiceSpec], Completion], self.apply_nfs),
             'node-exporter': self.apply_node_exporter,
-            'osd': self.apply_drivegroups,
+            'osd': cast(Callable[[ServiceSpec], Completion], lambda dg: self.apply_drivegroups([dg])),
             'prometheus': self.apply_prometheus,
             'rbd-mirror': self.apply_rbd_mirror,
-            'rgw': self.apply_rgw,
+            'rgw': cast(Callable[[ServiceSpec], Completion], self.apply_rgw),
         }
-        spec, [specs] = specs
 
-        completion = fns[spec.service_name](spec)
+        def merge(ls, r):
+            if isinstance(ls, list):
+                return ls + [r]
+            return [ls, r]
+
+        spec, *specs = specs
+
+        completion = fns[spec.service_type](spec)
         for s in specs:
-            completion.then(fns[spec.service_name](spec))
+            def next(ls):
+                return fns[s.service_type](s).then(lambda r: merge(ls, r))
+            completion = completion.then(next)
         return completion
 
     def remove_daemons(self, names):
diff --git a/src/pybind/mgr/tests/__init__.py b/src/pybind/mgr/tests/__init__.py
index e2d73534fed..680302e6afa 100644
--- a/src/pybind/mgr/tests/__init__.py
+++ b/src/pybind/mgr/tests/__init__.py
@@ -22,9 +22,14 @@ if 'UNITTEST' in os.environ:
             self._ceph_get_version = mock.Mock()
             self._ceph_get = mock.MagicMock()
             self._ceph_get_module_option = mock.MagicMock()
+            self._ceph_get_option = mock.MagicMock()
+            self._validate_module_option = lambda _: True
+            self._configure_logging = lambda *_: None
+            self._unconfigure_logging = mock.MagicMock()
             self._ceph_log = mock.MagicMock()
             self._ceph_get_store = lambda _: ''
             self._ceph_get_store_prefix = lambda _: {}
+            self._ceph_dispatch_remote = lambda *_: None
 
 
     cm = mock.Mock()
diff --git a/src/pybind/mgr/tests/test_orchestrator.py b/src/pybind/mgr/tests/test_orchestrator.py
index f627e070aa1..66d4474639c 100644
--- a/src/pybind/mgr/tests/test_orchestrator.py
+++ b/src/pybind/mgr/tests/test_orchestrator.py
@@ -1,5 +1,7 @@
 from __future__ import absolute_import
 
+from ceph.deployment.service_spec import ServiceSpec
+from test_orchestrator import TestOrchestrator as _TestOrchestrator
 from tests import mock
 
 import pytest
@@ -226,3 +228,12 @@ def test_pretty_print():
 
     assert p.result == 5
 
+def test_apply():
+    to = _TestOrchestrator('', 0, 0)
+    completion = to.apply([
+        ServiceSpec(service_type='nfs'),
+        ServiceSpec(service_type='nfs'),
+        ServiceSpec(service_type='nfs'),
+    ])
+    completion.finalize(42)
+    assert  completion.result == [None, None, None]
\ No newline at end of file