diff --git a/nova/cmd/manage.py b/nova/cmd/manage.py
index c6482e2b980c..f23b52cff584 100644
--- a/nova/cmd/manage.py
+++ b/nova/cmd/manage.py
@@ -38,6 +38,7 @@ from oslo_config import cfg
 from oslo_db import exception as db_exc
 from oslo_log import log as logging
 import oslo_messaging as messaging
+from oslo_serialization import jsonutils
 from oslo_utils import encodeutils
 from oslo_utils import importutils
 from oslo_utils import uuidutils
@@ -2168,16 +2169,19 @@ class PlacementCommands(object):
 
         if need_healing:
             if dry_run:
+                # json dump the allocation dict as it contains nested default
+                # dicts that is pretty hard to read in the verbose output
+                alloc = jsonutils.dumps(allocations)
                 if need_healing == _CREATE:
                     output(_('[dry-run] Create allocations for instance '
                              '%(instance)s: %(allocations)s') %
                            {'instance': instance.uuid,
-                            'allocations': allocations})
+                            'allocations': alloc})
                 elif need_healing == _UPDATE:
                     output(_('[dry-run] Update allocations for instance '
                              '%(instance)s: %(allocations)s') %
                            {'instance': instance.uuid,
-                            'allocations': allocations})
+                            'allocations': alloc})
             else:
                 # First update ports in neutron. If any of those operations
                 # fail, then roll back the successful part of it and fail the
diff --git a/nova/tests/functional/test_nova_manage.py b/nova/tests/functional/test_nova_manage.py
index d913c180ce70..2bdf3884ab3e 100644
--- a/nova/tests/functional/test_nova_manage.py
+++ b/nova/tests/functional/test_nova_manage.py
@@ -880,6 +880,25 @@ class TestNovaManagePlacementHealPortAllocations(
             self.output.getvalue())
         self.assertEqual(0, result)
 
+    def test_heal_port_allocation_dry_run(self):
+        server, ports = self._create_server_with_missing_port_alloc(
+            [self.neutron.port_1])
+
+        # let's trigger a heal
+        result = self.cli.heal_allocations(
+            verbose=True, max_count=2, dry_run=True)
+
+        self._assert_placement_not_updated(server)
+        self._assert_ports_not_updated(ports)
+
+        self.assertIn(
+            '[dry-run] Update allocations for instance',
+            self.output.getvalue())
+        # Note that we had a issues by printing defaultdicts directly to the
+        # user in the past. So let's assert it does not happen any more.
+        self.assertNotIn('defaultdict', self.output.getvalue())
+        self.assertEqual(4, result)
+
     def test_no_healing_is_needed(self):
         """Test that the instance has a port that has allocations
         so nothing to be healed.