diff --git a/tests/regression/test/issue-2639/regression.test.ts b/tests/regression/test/issue-2639/regression.test.ts
new file mode 100644
index 000000000..f90800681
--- /dev/null
+++ b/tests/regression/test/issue-2639/regression.test.ts
@@ -0,0 +1,38 @@
+import { createTestClient } from '@zenstackhq/testtools';
+import { createSchemaFactory } from '@zenstackhq/zod';
+import { describe, expectTypeOf, it } from 'vitest';
+import z from 'zod';
+import { schema } from './schema';
+
+// https://github.com/zenstackhq/zenstack/issues/2639
+//
+// The user reported that the type inferred from `factory.makeModelSchema('Test')`
+// was not assignable to the ORM-inferred model type because the zod-inferred
+// `metaData` field included `null` while the ORM `JsonValue` did not.
+
+const factory = createSchemaFactory(schema);
+
+describe('Regression for issue #2639', () => {
+    it('zod-inferred model type is assignable to the ORM model type', async () => {
+        const db = await createTestClient(schema);
+        const _schema = factory.makeModelSchema('Test');
+        type ZodTest = z.infer<typeof _schema>;
+        type OrmTest = Awaited<ReturnType<typeof db.test.findFirstOrThrow>>;
+
+        // Mirrors the user's reproduction:
+        //   function testFunction(test: OrmTest) {}
+        //   testFunction({} as ZodTest)
+        expectTypeOf<ZodTest>().toExtend<OrmTest>();
+    });
+
+    it('zod-inferred metaData allows null and is assignable to the ORM metaData', async () => {
+        const db = await createTestClient(schema);
+        const _schema = factory.makeModelSchema('Test');
+        type ZodTest = z.infer<typeof _schema>;
+        type OrmTest = Awaited<ReturnType<typeof db.test.findFirstOrThrow>>;
+
+        expectTypeOf<null>().toExtend<ZodTest['metaData']>();
+        expectTypeOf<null>().toExtend<OrmTest['metaData']>();
+        expectTypeOf<ZodTest['metaData']>().toExtend<OrmTest['metaData']>();
+    });
+});
diff --git a/tests/regression/test/issue-2639/schema.ts b/tests/regression/test/issue-2639/schema.ts
new file mode 100644
index 000000000..8e8088b86
--- /dev/null
+++ b/tests/regression/test/issue-2639/schema.ts
@@ -0,0 +1,86 @@
+//////////////////////////////////////////////////////////////////////////////////////////////
+// DO NOT MODIFY THIS FILE                                                                  //
+// This file is automatically generated by ZenStack CLI and should not be manually updated. //
+//////////////////////////////////////////////////////////////////////////////////////////////
+
+/* eslint-disable */
+
+import { type SchemaDef, type AttributeApplication, type FieldDefault, ExpressionUtils } from "@zenstackhq/schema";
+export class SchemaType implements SchemaDef {
+    provider = {
+        type: "postgresql"
+    } as const;
+    models = {
+        Test: {
+            name: "Test",
+            fields: {
+                id: {
+                    name: "id",
+                    type: "String",
+                    id: true,
+                    attributes: [{ name: "@id" }, { name: "@default", args: [{ name: "value", value: ExpressionUtils.call("uuid") }] }] as readonly AttributeApplication[],
+                    default: ExpressionUtils.call("uuid") as FieldDefault
+                },
+                createdAt: {
+                    name: "createdAt",
+                    type: "DateTime",
+                    attributes: [{ name: "@default", args: [{ name: "value", value: ExpressionUtils.call("now") }] }] as readonly AttributeApplication[],
+                    default: ExpressionUtils.call("now") as FieldDefault
+                },
+                updatedAt: {
+                    name: "updatedAt",
+                    type: "DateTime",
+                    updatedAt: true,
+                    attributes: [{ name: "@updatedAt" }] as readonly AttributeApplication[]
+                },
+                metaData: {
+                    name: "metaData",
+                    type: "Json",
+                    attributes: [{ name: "@default", args: [{ name: "value", value: ExpressionUtils.literal("{}") }] }] as readonly AttributeApplication[],
+                    default: "{}" as FieldDefault
+                },
+                name: {
+                    name: "name",
+                    type: "String"
+                }
+            },
+            idFields: ["id"],
+            uniqueFields: {
+                id: { type: "String" }
+            }
+        }
+    } as const;
+    typeDefs = {
+        BasicFields: {
+            name: "BasicFields",
+            fields: {
+                id: {
+                    name: "id",
+                    type: "String",
+                    attributes: [{ name: "@id" }, { name: "@default", args: [{ name: "value", value: ExpressionUtils.call("uuid") }] }] as readonly AttributeApplication[],
+                    default: ExpressionUtils.call("uuid") as FieldDefault
+                },
+                createdAt: {
+                    name: "createdAt",
+                    type: "DateTime",
+                    attributes: [{ name: "@default", args: [{ name: "value", value: ExpressionUtils.call("now") }] }] as readonly AttributeApplication[],
+                    default: ExpressionUtils.call("now") as FieldDefault
+                },
+                updatedAt: {
+                    name: "updatedAt",
+                    type: "DateTime",
+                    updatedAt: true,
+                    attributes: [{ name: "@updatedAt" }] as readonly AttributeApplication[]
+                },
+                metaData: {
+                    name: "metaData",
+                    type: "Json",
+                    attributes: [{ name: "@default", args: [{ name: "value", value: ExpressionUtils.literal("{}") }] }] as readonly AttributeApplication[],
+                    default: "{}" as FieldDefault
+                }
+            }
+        }
+    } as const;
+    plugins = {};
+}
+export const schema = new SchemaType();
diff --git a/tests/regression/test/issue-2639/schema.zmodel b/tests/regression/test/issue-2639/schema.zmodel
new file mode 100644
index 000000000..2a8c3387d
--- /dev/null
+++ b/tests/regression/test/issue-2639/schema.zmodel
@@ -0,0 +1,15 @@
+datasource db {
+    provider = 'postgresql'
+    url      = env("DATABASE_URL")
+}
+
+type BasicFields {
+    id        String   @id @default(uuid())
+    createdAt DateTime @default(now())
+    updatedAt DateTime @updatedAt
+    metaData  Json     @default("{}")
+}
+
+model Test with BasicFields {
+    name String
+}