diff --git a/tests/test_requests.py b/tests/test_requests.py
index 0948b09..0b19940 100644
--- a/tests/test_requests.py
+++ b/tests/test_requests.py
@@ -99,7 +99,7 @@ class TestRequestFactory(unittest.TestCase):
             full_url_pattern=url,
             method="get",
             parameters=RequestParameters(query=ImmutableMultiDict(parameters)),
-            body="",
+            body=b"",
             mimetype="application/x-www-form-urlencoded",
         )
         openapi_request = TornadoRequestFactory.create(tornado_request)
@@ -125,7 +125,7 @@ class TestRequestFactory(unittest.TestCase):
             full_url_pattern=url,
             method="get",
             parameters=RequestParameters(query=ImmutableMultiDict(parameters)),
-            body="",
+            body=b"",
             mimetype="application/x-www-form-urlencoded",
         )
         openapi_request = TornadoRequestFactory.create(tornado_request)
diff --git a/tests/test_responses.py b/tests/test_responses.py
index e953780..6d4ebd5 100644
--- a/tests/test_responses.py
+++ b/tests/test_responses.py
@@ -66,7 +66,7 @@ class TestResponseFactory(unittest.TestCase):
         tornado_request = HTTPRequest(url="http://example.com")
         tornado_response = HTTPResponse(request=tornado_request, code=200)
         expected = OpenAPIResponse(
-            data="",
+            data=b"",
             status_code=200,
             mimetype="text/html",
         )
diff --git a/tornado_openapi3/requests.py b/tornado_openapi3/requests.py
index 893bb7d..259f40c 100644
--- a/tornado_openapi3/requests.py
+++ b/tornado_openapi3/requests.py
@@ -43,7 +43,7 @@ class TornadoRequestFactory:
             parameters=RequestParameters(
                 query=query_arguments, header=Headers(request.headers.get_all())
             ),
-            body=request.body.decode("utf-8") if request.body else "",
+            body=request.body if request.body else b"",
             mimetype=request.headers.get(
                 "Content-Type", "application/x-www-form-urlencoded"
             ),
diff --git a/tornado_openapi3/responses.py b/tornado_openapi3/responses.py
index 534f246..fc87f4a 100644
--- a/tornado_openapi3/responses.py
+++ b/tornado_openapi3/responses.py
@@ -13,7 +13,7 @@ class TornadoResponseFactory:
     def create(cls, response: HTTPResponse) -> OpenAPIResponse:
         mimetype = response.headers.get("Content-Type", "text/html")
         return OpenAPIResponse(
-            data=response.body.decode("utf-8") if response.body else "",
+            data=response.body if response.body else b"",
             status_code=response.code,
             mimetype=mimetype,
         )