diff --git a/hooks/rabbitmq_context.py b/hooks/rabbitmq_context.py
index 95da30f6..8b67bcad 100644
--- a/hooks/rabbitmq_context.py
+++ b/hooks/rabbitmq_context.py
@@ -55,8 +55,11 @@ ENV_CONF = '/etc/rabbitmq/rabbitmq-env.conf'
 #              https://tinyurl.com/rabbitmq-3-5-7 for exact value. Note that
 #              this default has increased with newer versions so we should
 #              track this and keep the charm up-to-date.
+#              Also note that 1024 is the maximum supported number of
+#              threads.
 DEFAULT_MULTIPLIER = 24
 MAX_DEFAULT_THREADS = DEFAULT_MULTIPLIER * 2
+MAX_NUM_THREADS = 1024
 
 
 def convert_from_base64(v):
@@ -203,9 +206,9 @@ class RabbitMQEnvContext(object):
         Determine the number of erl vm threads in pool based in cpu resources
         available.
 
-        Number of threads will be limited to MAX_DEFAULT_WORKERS in
+        Number of threads will be limited to MAX_DEFAULT_THREADS in
         container environments where no worker-multipler configuration
-        option been set.
+        option been set and to MAX_NUM_THREADS in all other situations.
 
         @returns int: number of io threads to allocate
         """
@@ -231,6 +234,10 @@ class RabbitMQEnvContext(object):
             #              configuration in LXD containers on large servers.
             count = min(count, MAX_DEFAULT_THREADS)
 
+        # Never configure a number of threads above the MAX_NUM_THREADS since
+        # otherwise the daemon won't start.
+        count = min(count, MAX_NUM_THREADS)
+
         log("erl vm io thread pool size = {} (capped={})"
             .format(count, is_container()), DEBUG)
 
diff --git a/unit_tests/test_rabbitmq_context.py b/unit_tests/test_rabbitmq_context.py
index 0072bb72..cdae6beb 100644
--- a/unit_tests/test_rabbitmq_context.py
+++ b/unit_tests/test_rabbitmq_context.py
@@ -251,7 +251,7 @@ class TestRabbitMQEnvContext(unittest.TestCase):
                                   "'+A 48'"})
 
     @mock.patch.object(rabbitmq_context, 'relation_ids', lambda *args: [])
-    @mock.patch.object(rabbitmq_context.psutil, 'NUM_CPUS', 128)
+    @mock.patch.object(rabbitmq_context.psutil, 'NUM_CPUS', 40)
     @mock.patch.object(rabbitmq_context, 'service_name')
     @mock.patch.object(rabbitmq_context, 'config')
     def test_rabbitmqenv_in_container(self, mock_config, mock_service_name):
@@ -276,11 +276,35 @@ class TestRabbitMQEnvContext(unittest.TestCase):
             ctxt = rabbitmq_context.RabbitMQEnvContext()()
             self.assertEqual(ctxt['settings'],
                              {'RABBITMQ_SERVER_ADDITIONAL_ERL_ARGS':
-                              "'+A 3072'"})
+                              "'+A 960'"})
 
             del config['erl-vm-io-thread-multiplier']
             mock_is_ctnr.return_value = False
             ctxt = rabbitmq_context.RabbitMQEnvContext()()
             self.assertEqual(ctxt['settings'],
                              {'RABBITMQ_SERVER_ADDITIONAL_ERL_ARGS':
-                              "'+A 3072'"})
+                              "'+A 960'"})
+
+    @mock.patch.object(rabbitmq_context.psutil, 'NUM_CPUS', 48)
+    @mock.patch.object(rabbitmq_context, 'relation_ids', lambda *args: [])
+    @mock.patch.object(rabbitmq_context, 'service_name')
+    @mock.patch.object(rabbitmq_context, 'config')
+    def test_rabbitmqenv_max_num_threads(self, mock_config, mock_service_name):
+        config = {}
+
+        def fake_config(key):
+            return config.get(key)
+
+        mock_service_name.return_value = 'svc_foo'
+        mock_config.side_effect = fake_config
+
+        ctxt = rabbitmq_context.RabbitMQEnvContext()()
+        self.assertEqual(ctxt['settings'],
+                         {'RABBITMQ_SERVER_ADDITIONAL_ERL_ARGS':
+                          "'+A 1024'"})
+
+        config['erl-vm-io-thread-multiplier'] = 10
+        ctxt = rabbitmq_context.RabbitMQEnvContext()()
+        self.assertEqual(ctxt['settings'],
+                         {'RABBITMQ_SERVER_ADDITIONAL_ERL_ARGS':
+                          "'+A 480'"})
diff --git a/unit_tests/test_rabbitmq_server_relations.py b/unit_tests/test_rabbitmq_server_relations.py
index 3981affd..1d291349 100644
--- a/unit_tests/test_rabbitmq_server_relations.py
+++ b/unit_tests/test_rabbitmq_server_relations.py
@@ -326,6 +326,8 @@ class RelationUtil(CharmTestCase):
             if os.path.exists(tmpdir):
                 shutil.rmtree(tmpdir)
 
+    @patch('rabbit_utils.lsb_release')
+    @patch.object(rabbitmq_server_relations.rabbit, 'grant_permissions')
     @patch('rabbit_utils.create_user')
     @patch('rabbit_utils.local_unit')
     @patch('rabbit_utils.nrpe.NRPE.add_check')
@@ -355,7 +357,9 @@ class RelationUtil(CharmTestCase):
                                 mock_check_call,
                                 mock_remove_check, mock_add_check,
                                 mock_local_unit,
-                                mock_create_user):
+                                mock_create_user,
+                                mock_grant_permissions,
+                                mock_lsb_release):
 
         self.test_config.set('ssl', 'on')
 
@@ -375,6 +379,7 @@ class RelationUtil(CharmTestCase):
         mock_nrpe_relation_ids.side_effect = lambda x: [
             'nrpe-external-master:1']
         mock_local_unit.return_value = 'unit/0'
+        mock_lsb_release.return_value = {'DISTRIB_CODENAME': 'focal'}
 
         rabbitmq_server_relations.update_nrpe_checks()
         mock_check_output.assert_any_call(