diff --git a/frontik/frontik_response.py b/frontik/frontik_response.py
index e532be4dc..351891a2f 100644
--- a/frontik/frontik_response.py
+++ b/frontik/frontik_response.py
@@ -17,8 +17,13 @@ def __init__(
         body: bytes = b'',
     ):
         self.headers = HTTPHeaders(get_default_headers())  # type: ignore
-        if headers is not None:
+
+        if isinstance(headers, HTTPHeaders):
+            for k, v in headers.get_all():
+                self.headers.add(k, v)
+        elif headers is not None:
             self.headers.update(headers)
+
         self.status_code = status_code
         self.body = body
         self.data_written = False
diff --git a/tests/test_cookies.py b/tests/test_cookies.py
new file mode 100644
index 000000000..689944bc7
--- /dev/null
+++ b/tests/test_cookies.py
@@ -0,0 +1,40 @@
+import pytest
+from fastapi import Response
+
+from frontik.app import FrontikApplication
+from frontik.handler import PageHandler, get_current_handler
+from frontik.routing import plain_router
+from frontik.testing import FrontikTestBase
+
+
+@plain_router.get('/cookies', cls=PageHandler)
+async def cookies_page(handler: PageHandler = get_current_handler()) -> None:
+    handler.set_cookie('key1', 'val1')
+    handler.set_cookie('key2', 'val2')
+
+
+@plain_router.get('/asgi_cookies')
+async def asgi_cookies_page(response: Response) -> None:
+    response.set_cookie('key1', 'val1')
+    response.set_cookie('key2', 'val2')
+
+
+class TestFrontikTesting(FrontikTestBase):
+    @pytest.fixture(scope='class')
+    def frontik_app(self) -> FrontikApplication:
+        return FrontikApplication()
+
+    async def test_cookies(self):
+        response = await self.fetch('/cookies')
+
+        assert response.status_code == 200
+        assert response.headers.getall('Set-Cookie') == ['key1=val1; Path=/', 'key2=val2; Path=/']
+
+    async def test_asgi_cookies(self):
+        response = await self.fetch('/asgi_cookies')
+
+        assert response.status_code == 200
+        assert response.headers.getall('Set-Cookie') == [
+            'key1=val1; Path=/; SameSite=lax',
+            'key2=val2; Path=/; SameSite=lax',
+        ]