diff --git a/integration/testdata/duration/functions/createDurationInHook.ts b/integration/testdata/duration/functions/createDurationInHook.ts
new file mode 100755
index 000000000..e12070500
--- /dev/null
+++ b/integration/testdata/duration/functions/createDurationInHook.ts
@@ -0,0 +1,13 @@
+import { CreateDurationInHook, CreateDurationInHookHooks, Duration } from '@teamkeel/sdk';
+
+// To learn more about what you can do with hooks, visit https://docs.keel.so/functions
+const hooks: CreateDurationInHookHooks = {
+    beforeWrite: async (ctx, inputs) => {
+        return {
+            dur: Duration.fromISOString("PT1H")
+        }
+    },
+};
+
+export default CreateDurationInHook(hooks);
+	
\ No newline at end of file
diff --git a/integration/testdata/duration/functions/writeCustomFunction.ts b/integration/testdata/duration/functions/writeCustomFunction.ts
new file mode 100755
index 000000000..a5362f2af
--- /dev/null
+++ b/integration/testdata/duration/functions/writeCustomFunction.ts
@@ -0,0 +1,9 @@
+import { WriteCustomFunction, models } from '@teamkeel/sdk';
+
+// To learn more about what you can do with custom functions, visit https://docs.keel.so/functions
+export default WriteCustomFunction(async (ctx, inputs) => {
+    const mod = await models.myDuration.create({ dur: inputs.dur })
+    return {
+        model: mod
+    }
+});
diff --git a/integration/testdata/duration/schema.keel b/integration/testdata/duration/schema.keel
new file mode 100644
index 000000000..d03667249
--- /dev/null
+++ b/integration/testdata/duration/schema.keel
@@ -0,0 +1,31 @@
+model MyDuration {
+    fields {
+        dur Duration?
+    }
+    actions {
+        create createDuration() with (dur)
+        update updateDuration(id) with (dur)
+        get getDuration(id)
+        list listDurations() {
+            @orderBy(createdAt: asc)
+        }
+        create createDurationInHook() @function 
+        write writeCustomFunction(DurationMessage) returns (ModelMessage) {
+            @permission(expression: true)
+        }
+    }
+
+    @permission(expression: true, actions: [get, list, create, update])
+}
+
+message NestedDurationMessage {
+    msg DurationMessage
+}
+
+message DurationMessage {
+    dur Duration
+}
+
+message ModelMessage {
+    model MyDuration
+}
diff --git a/integration/testdata/duration/tests.test.ts b/integration/testdata/duration/tests.test.ts
new file mode 100644
index 000000000..718b4c4e8
--- /dev/null
+++ b/integration/testdata/duration/tests.test.ts
@@ -0,0 +1,60 @@
+import { actions, resetDatabase, models } from "@teamkeel/testing";
+import { beforeEach, expect, test } from "vitest";
+import { useDatabase, Duration } from "@teamkeel/sdk";
+import { sql } from "kysely";
+
+beforeEach(resetDatabase);
+
+test("duration - create action with duration input", async () => {
+  const result = await actions.createDuration({
+    dur: Duration.fromISOString("PT2H3M4S"),
+  });
+
+  expect(result.dur).toEqual("PT2H3M4S");
+});
+
+test("duration - update action with duration input", async () => {
+  const result = await actions.createDuration({
+    dur: Duration.fromISOString("PT2H3M4S"),
+  });
+
+  const updated = await actions.updateDuration({
+    where: {
+      id: result.id,
+    },
+    values: {
+      dur: Duration.fromISOString("PT1S"),
+    },
+  });
+
+  expect(updated.dur).toEqual("PT1S");
+});
+
+test("duration - write custom function", async () => {
+  const result = await actions.writeCustomFunction({
+    dur: Duration.fromISOString("PT1H2M3S"),
+  });
+
+  expect(result.model.dur).toEqual("PT1H2M3S");
+
+   const mydurs = await useDatabase()
+    .selectFrom("my_duration")
+    .selectAll()
+    .execute();
+
+  expect(mydurs.length).toEqual(1);
+  expect(mydurs[0].id).toEqual(result.model.id);
+  expect(mydurs[0].dur?.toISOString()).toEqual("PT1H2M3S");
+});
+
+test("durs - create and store duration in hook", async () => {
+  await actions.createDurationInHook({});
+
+  const mydurs = await useDatabase()
+    .selectFrom("my_duration")
+    .selectAll()
+    .execute();
+
+  expect(mydurs.length).toEqual(1);
+  expect(mydurs[0].dur?.toISOString()).toEqual("PT1H");
+});
diff --git a/packages/functions-runtime/src/Duration.js b/packages/functions-runtime/src/Duration.js
index b4e6975b4..6940a5a93 100644
--- a/packages/functions-runtime/src/Duration.js
+++ b/packages/functions-runtime/src/Duration.js
@@ -5,6 +5,8 @@ const isoRegex =
 
 class Duration {
   constructor(postgresString) {
+    this._typename = "Duration";
+    this.pgInterval = postgresString;
     this._interval = parseInterval(postgresString);
   }
 
diff --git a/packages/functions-runtime/src/database.js b/packages/functions-runtime/src/database.js
index fd36ceff7..c852335ec 100644
--- a/packages/functions-runtime/src/database.js
+++ b/packages/functions-runtime/src/database.js
@@ -78,7 +78,9 @@ function createDatabaseClient({ connString } = {}) {
       // https://kysely-org.github.io/kysely/classes/CamelCasePlugin.html
       // If they don't, then we can create a custom implementation of the plugin where we control
       // the casing behaviour (see url above for example)
-      new CamelCasePlugin(),
+      new CamelCasePlugin({
+        maintainNestedObjectKeys: true,
+      }),
     ],
     log(event) {
       if ("DEBUG" in process.env) {
@@ -153,10 +155,7 @@ function getDialect(connString) {
       // Adding a custom type parser for interval fields: see https://kysely.dev/docs/recipes/data-types#configuring-runtime-javascript-types
       // 1186 = type for INTERVAL
       pg.types.setTypeParser(1186, function (val) {
-        return {
-          _Typename: "Duration",
-          pgInterval: val,
-        };
+        return new Duration(val);
       });
 
       return new PostgresDialect({
@@ -194,10 +193,7 @@ function getDialect(connString) {
       // Adding a custom type parser for interval fields: see https://kysely.dev/docs/recipes/data-types#configuring-runtime-javascript-types
       // 1186 = type for INTERVAL
       neonserverless.types.setTypeParser(1186, function (val) {
-        return {
-          _Typename: "Duration",
-          pgInterval: val,
-        };
+        return new Duration(val);
       });
 
       neonserverless.neonConfig.webSocketConstructor = ws;
diff --git a/packages/functions-runtime/src/parsing.js b/packages/functions-runtime/src/parsing.js
index 5c269484b..395dcbda6 100644
--- a/packages/functions-runtime/src/parsing.js
+++ b/packages/functions-runtime/src/parsing.js
@@ -60,7 +60,7 @@ function transformRichDataTypes(data) {
   for (const key of keys) {
     const value = data[key];
     if (isPlainObject(value)) {
-      if (value._Typename == "Duration" && value.pgInterval) {
+      if (value._typename == "Duration" && value.pgInterval) {
         row[key] = new Duration(value.pgInterval);
       } else if (
         value.key &&