diff --git a/latest_migrations.manifest b/latest_migrations.manifest
index dac9ed4ce4539..ede9b35bf2662 100644
--- a/latest_migrations.manifest
+++ b/latest_migrations.manifest
@@ -5,7 +5,7 @@ contenttypes: 0002_remove_content_type_name
 ee: 0016_rolemembership_organization_member
 otp_static: 0002_throttling
 otp_totp: 0002_auto_20190420_0723
-posthog: 0403_plugin_has_private_access
+posthog: 0404_remove_propertydefinition_property_type_is_valid_and_more
 sessions: 0001_initial
 social_django: 0010_uid_db_index
 two_factor: 0007_auto_20201201_1019
diff --git a/mypy-baseline.txt b/mypy-baseline.txt
index 3c6bbf22089c0..9b607b6222cd3 100644
--- a/mypy-baseline.txt
+++ b/mypy-baseline.txt
@@ -366,6 +366,7 @@ posthog/session_recordings/queries/session_recording_list_from_replay_summary.py
 posthog/session_recordings/queries/session_recording_list_from_replay_summary.py:0: note: If the method is meant to be abstract, use @abc.abstractmethod
 posthog/session_recordings/queries/session_recording_list_from_replay_summary.py:0: error: Missing return statement  [empty-body]
 posthog/session_recordings/queries/session_recording_list_from_replay_summary.py:0: note: If the method is meant to be abstract, use @abc.abstractmethod
+posthog/migrations/0404_remove_propertydefinition_property_type_is_valid_and_more.py:0: error: Module "django.contrib.postgres.operations" has no attribute "AddConstraintNotValid"  [attr-defined]
 posthog/hogql_queries/test/test_query_runner.py:0: error: Variable "TestQueryRunner" is not valid as a type  [valid-type]
 posthog/hogql_queries/test/test_query_runner.py:0: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
 posthog/hogql_queries/test/test_query_runner.py:0: error: Invalid base class "TestQueryRunner"  [misc]
diff --git a/posthog/migrations/0404_remove_propertydefinition_property_type_is_valid_and_more.py b/posthog/migrations/0404_remove_propertydefinition_property_type_is_valid_and_more.py
new file mode 100644
index 0000000000000..ac34ed62af7b9
--- /dev/null
+++ b/posthog/migrations/0404_remove_propertydefinition_property_type_is_valid_and_more.py
@@ -0,0 +1,47 @@
+# Generated by Django 4.2.11 on 2024-04-21 21:11
+from django.contrib.postgres.operations import AddConstraintNotValid
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("posthog", "0403_plugin_has_private_access"),
+    ]
+
+    operations = [
+        migrations.RemoveConstraint(
+            model_name="propertydefinition",
+            name="property_type_is_valid",
+        ),
+        migrations.AlterField(
+            model_name="propertydefinition",
+            name="property_type",
+            field=models.CharField(
+                blank=True,
+                choices=[
+                    ("DateTime", "DateTime"),
+                    ("String", "String"),
+                    ("Numeric", "Numeric"),
+                    ("Boolean", "Boolean"),
+                    ("Duration", "Duration"),
+                ],
+                max_length=50,
+                null=True,
+            ),
+        ),
+        migrations.AlterField(
+            model_name="propertydefinition",
+            name="type",
+            field=models.PositiveSmallIntegerField(
+                choices=[(1, "event"), (2, "person"), (3, "group"), (4, "session")], default=1
+            ),
+        ),
+        # changed from migrations.AddConstraint. See migration 0405 for where we validate the constraint
+        AddConstraintNotValid(
+            model_name="propertydefinition",
+            constraint=models.CheckConstraint(
+                check=models.Q(("property_type__in", ["DateTime", "String", "Numeric", "Boolean", "Duration"])),
+                name="property_type_is_valid",
+            ),
+        ),
+    ]
diff --git a/posthog/models/property_definition.py b/posthog/models/property_definition.py
index 0a6f89354a639..8c8b9d6c773b4 100644
--- a/posthog/models/property_definition.py
+++ b/posthog/models/property_definition.py
@@ -12,6 +12,7 @@ class PropertyType(models.TextChoices):
     String = "String", "String"
     Numeric = "Numeric", "Numeric"
     Boolean = "Boolean", "Boolean"
+    Duration = "Duration", "Duration"
 
 
 class PropertyFormat(models.TextChoices):
@@ -34,6 +35,7 @@ class Type(models.IntegerChoices):
         EVENT = 1, "event"
         PERSON = 2, "person"
         GROUP = 3, "group"
+        SESSION = 4, "session"
 
     team: models.ForeignKey = models.ForeignKey(
         Team,