diff --git a/.circleci/config.yml b/.circleci/config.yml
index f33121db..4153459f 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -49,7 +49,8 @@ jobs:
       - run:
           name: install requirements
           command: |
-            sudo pip install --upgrade pip virtualenv;
+            sudo pip install --upgrade pip;
+            sudo pip install 'virtualenv~=16.0';
             sudo pip install -r test-requirements.txt;
             sudo pip install -r test-filesource-optional-requirements.txt;
             sudo pip install -r consul-requirements.txt;
diff --git a/CHANGELOG.md b/CHANGELOG.md
index e593c823..fd0d1ec3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,9 @@ This major release is for Python compatibility updates and removal of deprecated
 - Removed the individual HTTP-related parameters such as `connect_timeout` from the [`Config`](https://launchdarkly-python-sdk.readthedocs.io/en/latest/api-main.html#ldclient.config.Config) type. The correct way to set these now is with the [`HTTPConfig`](https://launchdarkly-python-sdk.readthedocs.io/en/latest/api-main.html#ldclient.config.HTTPConfig) sub-configuration object: `Config(sdk_key = "my-sdk-key", http = HTTPConfig(connect_timeout = 10))`.
 - Removed all other types, parameters, and methods that were deprecated as of the last 6.x release.
 
+## [6.13.3] - 2021-02-23
+### Fixed:
+- The SDK could fail to send debug events when event debugging was enabled on the LaunchDarkly dashboard, if the application server's time zone was not GMT.
 
 ## [6.13.2] - 2020-09-21
 ### Fixed:
diff --git a/ldclient/client.py b/ldclient/client.py
index c97bbb42..d401df39 100644
--- a/ldclient/client.py
+++ b/ldclient/client.py
@@ -187,6 +187,25 @@ def track(self, event_name: str, user: dict, data: Optional[Any]=None, metric_va
         else:
             self._send_event(self._event_factory_default.new_custom_event(event_name, user, data, metric_value))
 
+    def alias(self, current_user: dict, previous_user: dict):
+        """Associates two users for analytics purposes.
+
+        This can be helpful in the situation where a person is represented by multiple
+        LaunchDarkly users. This may happen, for example, when a person initially logs into
+        an application, the person might be represented by an anonymous user prior to logging
+        in and a different user after logging in, as denoted by a different user key.
+
+        :param current_user: The new version of a user.
+        :param previous_user: The old version of a user.
+        """
+        if current_user is None or current_user.get('key') is None:
+            log.warning("Missing current_user or current_user key when calling alias().")
+            return None
+        if previous_user is None or previous_user.get('key') is None:
+            log.warning("Missing previous_user or previous_user key when calling alias().")
+            return None
+        self._send_event(self._event_factory_default.new_alias_event(current_user, previous_user))
+
     def identify(self, user: dict):
         """Registers the user.
 
diff --git a/ldclient/event_processor.py b/ldclient/event_processor.py
index 6174f7f2..1afb3221 100644
--- a/ldclient/event_processor.py
+++ b/ldclient/event_processor.py
@@ -65,6 +65,8 @@ def make_output_event(self, e):
                 out['userKey'] = self._get_userkey(e)
             if e.get('reason'):
                 out['reason'] = e.get('reason')
+            if e.get('contextKind'):
+                out['contextKind'] = e.get('contextKind')
             return out
         elif kind == 'identify':
             return {
@@ -87,6 +89,8 @@ def make_output_event(self, e):
                 out['data'] = e['data']
             if e.get('metricValue') is not None:
                 out['metricValue'] = e['metricValue']
+            if e.get('contextKind'):
+                out['contextKind'] = e.get('contextKind')
             return out
         elif kind == 'index':
             return {
diff --git a/ldclient/impl/event_factory.py b/ldclient/impl/event_factory.py
index c35d3bbe..16f81ac7 100644
--- a/ldclient/impl/event_factory.py
+++ b/ldclient/impl/event_factory.py
@@ -30,6 +30,8 @@ def new_eval_event(self, flag, user, detail, default_value, prereq_of_flag = Non
             e['prereqOf'] = prereq_of_flag.get('key')
         if add_experiment_data or self._with_reasons:
             e['reason'] = detail.reason
+        if user is not None and user.get('anonymous'):
+            e['contextKind'] = self._user_to_context_kind(user)
         return e
 
     def new_default_event(self, flag, user, default_value, reason):
@@ -48,6 +50,8 @@ def new_default_event(self, flag, user, default_value, reason):
             e['debugEventsUntilDate'] = flag.get('debugEventsUntilDate')
         if self._with_reasons:
             e['reason'] = reason
+        if user is not None and user.get('anonymous'):
+            e['contextKind'] = self._user_to_context_kind(user)
         return e
 
     def new_unknown_flag_event(self, key, user, default_value, reason):
@@ -60,6 +64,8 @@ def new_unknown_flag_event(self, key, user, default_value, reason):
         }
         if self._with_reasons:
             e['reason'] = reason
+        if user is not None and user.get('anonymous'):
+            e['contextKind'] = self._user_to_context_kind(user)
         return e
 
     def new_identify_event(self, user):
@@ -79,8 +85,25 @@ def new_custom_event(self, event_name, user, data, metric_value):
             e['data'] = data
         if metric_value is not None:
             e['metricValue'] = metric_value
+        if user.get('anonymous'):
+            e['contextKind'] = self._user_to_context_kind(user)
         return e
 
+    def new_alias_event(self, current_user, previous_user):
+        return {
+            'kind': 'alias',
+            'key': current_user.get('key'),
+            'contextKind': self._user_to_context_kind(current_user),
+            'previousKey': previous_user.get('key'),
+            'previousContextKind': self._user_to_context_kind(previous_user)
+        }
+
+    def _user_to_context_kind(self, user):
+        if user.get('anonymous'):
+            return "anonymousUser"
+        else:
+            return "user"
+
     def _is_experiment(self, flag, reason):
         if reason is not None:
             kind = reason['kind']
diff --git a/test-filesource-optional-requirements.txt b/test-filesource-optional-requirements.txt
index 40e04279..3cfa747b 100644
--- a/test-filesource-optional-requirements.txt
+++ b/test-filesource-optional-requirements.txt
@@ -1,2 +1,2 @@
 pyyaml>=3.0,<5.2
-watchdog>=0.9
+watchdog>=0.9,<1.0
diff --git a/test-requirements.txt b/test-requirements.txt
index 1f80fcc7..93da9126 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,7 +1,7 @@
 mock>=2.0.0
 pytest>=2.8
-redis>=2.10.5
-boto3>=1.9.71
+redis>=2.10.5,<3.0.0
+boto3>=1.9.71,<2.0.0
 coverage>=4.4
 jsonpickle==0.9.3
 pytest-cov>=2.4.0
diff --git a/testing/test_ldclient.py b/testing/test_ldclient.py
index 7615bb16..86cc319e 100644
--- a/testing/test_ldclient.py
+++ b/testing/test_ldclient.py
@@ -24,6 +24,10 @@
     }
 }
 
+anonymous_user = {
+    u'key': u'abc',
+    u'anonymous': True
+}
 
 def make_client(store = InMemoryFeatureStore()):
     return LDClient(config=Config(sdk_key = 'SDK_KEY',
@@ -172,6 +176,26 @@ def test_track_no_user_key():
         assert count_events(client) == 0
 
 
+def test_track_anonymous_user():
+    with make_client() as client:
+        client.track('my_event', anonymous_user)
+        e = get_first_event(client)
+        assert e['kind'] == 'custom' and e['key'] == 'my_event' and e['user'] == anonymous_user and e.get('data') is None and e.get('metricValue') is None and e.get('contextKind') == 'anonymousUser'
+
+
+def test_alias():
+    with make_client() as client:
+        client.alias(user, anonymous_user)
+        e = get_first_event(client)
+        assert e['kind'] == 'alias' and e['key'] == 'xyz' and e['contextKind'] == 'user' and e['previousKey'] == 'abc' and e['previousContextKind'] == 'anonymousUser'
+
+
+def test_alias_no_user():
+    with make_client() as client:
+        client.alias(None, None)
+        assert count_events(client) == 0
+
+
 def test_defaults():
     config=Config("SDK_KEY", base_uri="http://localhost:3000", defaults={"foo": "bar"}, offline=True)
     with LDClient(config=config) as client:
@@ -226,7 +250,30 @@ def test_event_for_existing_feature():
             e.get('reason') is None and
             e['default'] == 'default' and
             e['trackEvents'] == True and
-            e['debugEventsUntilDate'] == 1000)
+            e['debugEventsUntilDate'] == 1000 and
+            e.get('contextKind') is None)
+
+
+def test_event_for_existing_feature_anonymous_user():
+    feature = make_off_flag_with_value('feature.key', 'value')
+    feature['trackEvents'] = True
+    feature['debugEventsUntilDate'] = 1000
+    store = InMemoryFeatureStore()
+    store.init({FEATURES: {'feature.key': feature}})
+    with make_client(store) as client:
+        assert 'value' == client.variation('feature.key', anonymous_user, default='default')
+        e = get_first_event(client)
+        assert (e['kind'] == 'feature' and
+            e['key'] == 'feature.key' and
+            e['user'] == anonymous_user and
+            e['version'] == feature['version'] and
+            e['value'] == 'value' and
+            e['variation'] == 0 and
+            e.get('reason') is None and
+            e['default'] == 'default' and
+            e['trackEvents'] == True and
+            e['debugEventsUntilDate'] == 1000 and
+            e['contextKind'] == 'anonymousUser')
 
 
 def test_event_for_existing_feature_with_reason():