diff --git a/openapi_core/casting/schemas/exceptions.py b/openapi_core/casting/schemas/exceptions.py
index cc10672a..aa50b3f9 100644
--- a/openapi_core/casting/schemas/exceptions.py
+++ b/openapi_core/casting/schemas/exceptions.py
@@ -1,13 +1,13 @@
-import attr
+from dataclasses import dataclass
 
 from openapi_core.exceptions import OpenAPIError
 
 
-@attr.s(hash=True)
+@dataclass
 class CastError(OpenAPIError):
     """Schema cast operation error"""
-    value = attr.ib()
-    type = attr.ib()
+    value: str
+    type: str
 
     def __str__(self):
         return "Failed to cast value {value} to type {type}".format(
diff --git a/openapi_core/contrib/django/requests.py b/openapi_core/contrib/django/requests.py
index b8624bd6..d067ce55 100644
--- a/openapi_core/contrib/django/requests.py
+++ b/openapi_core/contrib/django/requests.py
@@ -1,8 +1,9 @@
 """OpenAPI core contrib django requests module"""
 import re
-
 from urllib.parse import urljoin
 
+from werkzeug.datastructures import ImmutableMultiDict, Headers
+
 from openapi_core.contrib.django.compat import (
     get_request_headers, get_current_scheme_host,
 )
@@ -43,13 +44,16 @@ def create(cls, request):
                 route = route[:-1]
             path_pattern = '/' + route
 
+        request_headers = get_request_headers(request)
         path = request.resolver_match and request.resolver_match.kwargs or {}
-        headers = get_request_headers(request)
+        query = ImmutableMultiDict(request.GET)
+        header = Headers(request_headers.items())
+        cookie = ImmutableMultiDict(dict(request.COOKIES))
         parameters = RequestParameters(
             path=path,
-            query=request.GET,
-            header=list(headers.items()),
-            cookie=request.COOKIES,
+            query=query,
+            header=header,
+            cookie=cookie,
         )
         current_scheme_host = get_current_scheme_host(request)
         full_url_pattern = urljoin(current_scheme_host, path_pattern)
diff --git a/openapi_core/contrib/django/responses.py b/openapi_core/contrib/django/responses.py
index d0e75f79..d32c7566 100644
--- a/openapi_core/contrib/django/responses.py
+++ b/openapi_core/contrib/django/responses.py
@@ -1,4 +1,6 @@
 """OpenAPI core contrib django responses module"""
+from werkzeug.datastructures import Headers
+
 from openapi_core.contrib.django.compat import get_response_headers
 from openapi_core.validation.response.datatypes import OpenAPIResponse
 
@@ -9,9 +11,10 @@ class DjangoOpenAPIResponseFactory:
     def create(cls, response):
         mimetype = response["Content-Type"]
         headers = get_response_headers(response)
+        header = Headers(headers.items())
         return OpenAPIResponse(
             data=response.content,
             status_code=response.status_code,
-            headers=list(headers.items()),
+            headers=header,
             mimetype=mimetype,
         )
diff --git a/openapi_core/contrib/falcon/requests.py b/openapi_core/contrib/falcon/requests.py
index 27a5faba..9f6b5292 100644
--- a/openapi_core/contrib/falcon/requests.py
+++ b/openapi_core/contrib/falcon/requests.py
@@ -1,7 +1,7 @@
 """OpenAPI core contrib falcon responses module"""
 from json import dumps
 
-from werkzeug.datastructures import ImmutableMultiDict
+from werkzeug.datastructures import ImmutableMultiDict, Headers
 
 from openapi_core.contrib.falcon.compat import get_request_media
 from openapi_core.validation.request.datatypes import (
@@ -29,11 +29,12 @@ def create(cls, request, default_when_empty={}):
             mimetype = request.content_type.partition(";")[0]
 
         query = ImmutableMultiDict(list(request.params.items()))
+        header = Headers(request.headers)
 
         # Path gets deduced by path finder against spec
         parameters = RequestParameters(
             query=query,
-            header=request.headers,
+            header=header,
             cookie=request.cookies,
         )
         url_pattern = request.prefix + request.path
diff --git a/openapi_core/contrib/falcon/responses.py b/openapi_core/contrib/falcon/responses.py
index b0477956..f99da684 100644
--- a/openapi_core/contrib/falcon/responses.py
+++ b/openapi_core/contrib/falcon/responses.py
@@ -1,4 +1,6 @@
 """OpenAPI core contrib falcon responses module"""
+from werkzeug.datastructures import Headers
+
 from openapi_core.contrib.falcon.compat import get_response_text
 from openapi_core.validation.response.datatypes import OpenAPIResponse
 
@@ -15,10 +17,11 @@ def create(cls, response):
             mimetype = response.options.default_media_type
 
         data = get_response_text(response)
+        headers = Headers(response.headers)
 
         return OpenAPIResponse(
             data=data,
             status_code=status_code,
-            headers=response.headers,
+            headers=headers,
             mimetype=mimetype,
         )
diff --git a/openapi_core/contrib/flask/requests.py b/openapi_core/contrib/flask/requests.py
index 7b4ec3bf..6fb9f367 100644
--- a/openapi_core/contrib/flask/requests.py
+++ b/openapi_core/contrib/flask/requests.py
@@ -1,8 +1,9 @@
 """OpenAPI core contrib flask requests module"""
 import re
-
 from urllib.parse import urljoin
 
+from werkzeug.datastructures import Headers
+
 from openapi_core.validation.request.datatypes import (
     RequestParameters, OpenAPIRequest,
 )
@@ -24,10 +25,11 @@ def create(cls, request):
         else:
             path_pattern = cls.path_regex.sub(r'{\1}', request.url_rule.rule)
 
+        header = Headers(request.headers)
         parameters = RequestParameters(
             path=request.view_args,
             query=request.args,
-            header=request.headers,
+            header=header,
             cookie=request.cookies,
         )
         full_url_pattern = urljoin(request.host_url, path_pattern)
diff --git a/openapi_core/contrib/flask/responses.py b/openapi_core/contrib/flask/responses.py
index cb52f5c1..a36a36ac 100644
--- a/openapi_core/contrib/flask/responses.py
+++ b/openapi_core/contrib/flask/responses.py
@@ -1,4 +1,6 @@
 """OpenAPI core contrib flask responses module"""
+from werkzeug.datastructures import Headers
+
 from openapi_core.validation.response.datatypes import OpenAPIResponse
 
 
@@ -6,9 +8,10 @@ class FlaskOpenAPIResponseFactory:
 
     @classmethod
     def create(cls, response):
+        header = Headers(response.headers)
         return OpenAPIResponse(
             data=response.data,
             status_code=response._status_code,
-            headers=response.headers,
+            headers=header,
             mimetype=response.mimetype,
         )
diff --git a/openapi_core/contrib/requests/requests.py b/openapi_core/contrib/requests/requests.py
index 49c74f5d..7f20f2b9 100644
--- a/openapi_core/contrib/requests/requests.py
+++ b/openapi_core/contrib/requests/requests.py
@@ -2,7 +2,7 @@
 
 from urllib.parse import urlparse, parse_qs
 
-from werkzeug.datastructures import ImmutableMultiDict
+from werkzeug.datastructures import ImmutableMultiDict, Headers
 from requests import Request
 
 from openapi_core.validation.request.datatypes import (
@@ -43,9 +43,9 @@ def create(cls, request):
         mimetype = request.headers.get('Content-Type') or \
             request.headers.get('Accept')
 
-        # Headers - request.headers is not an instance of dict
+        # Headers - request.headers is not an instance of Headers
         # which is expected
-        header = dict(request.headers)
+        header = Headers(dict(request.headers))
 
         # Body
         # TODO: figure out if request._body_position is relevant
diff --git a/openapi_core/contrib/requests/responses.py b/openapi_core/contrib/requests/responses.py
index c7d3359e..47725a5e 100644
--- a/openapi_core/contrib/requests/responses.py
+++ b/openapi_core/contrib/requests/responses.py
@@ -1,4 +1,6 @@
 """OpenAPI core contrib requests responses module"""
+from werkzeug.datastructures import Headers
+
 from openapi_core.validation.response.datatypes import OpenAPIResponse
 
 
@@ -7,7 +9,7 @@ class RequestsOpenAPIResponseFactory:
     @classmethod
     def create(cls, response):
         mimetype = response.headers.get('Content-Type')
-        headers = dict(response.headers)
+        headers = Headers(dict(response.headers))
         return OpenAPIResponse(
             data=response.content,
             status_code=response.status_code,
diff --git a/openapi_core/deserializing/exceptions.py b/openapi_core/deserializing/exceptions.py
index 2ff5774e..b8ae2ed3 100644
--- a/openapi_core/deserializing/exceptions.py
+++ b/openapi_core/deserializing/exceptions.py
@@ -1,13 +1,13 @@
-import attr
+from dataclasses import dataclass
 
 from openapi_core.exceptions import OpenAPIError
 
 
-@attr.s(hash=True)
+@dataclass
 class DeserializeError(OpenAPIError):
     """Deserialize operation error"""
-    value = attr.ib()
-    style = attr.ib()
+    value: str
+    style: str
 
     def __str__(self):
         return "Failed to deserialize value {value} with style {style}".format(
diff --git a/openapi_core/deserializing/parameters/exceptions.py b/openapi_core/deserializing/parameters/exceptions.py
index 6187f2c0..0966d93e 100644
--- a/openapi_core/deserializing/parameters/exceptions.py
+++ b/openapi_core/deserializing/parameters/exceptions.py
@@ -1,11 +1,11 @@
-import attr
+from dataclasses import dataclass
 
 from openapi_core.deserializing.exceptions import DeserializeError
 
 
-@attr.s(hash=True)
+@dataclass
 class EmptyParameterValue(DeserializeError):
-    name = attr.ib()
+    name: str
 
     def __str__(self):
         return "Value of parameter cannot be empty: {0}".format(self.name)
diff --git a/openapi_core/exceptions.py b/openapi_core/exceptions.py
index bdc5eba0..4fcf4d02 100644
--- a/openapi_core/exceptions.py
+++ b/openapi_core/exceptions.py
@@ -1,5 +1,8 @@
 """OpenAPI core exceptions module"""
-import attr
+from dataclasses import dataclass
+
+from openapi_core.validation.request.datatypes import OpenAPIRequest
+from openapi_core.validation.response.datatypes import OpenAPIResponse
 
 
 class OpenAPIError(Exception):
@@ -15,18 +18,18 @@ class MissingHeaderError(OpenAPIHeaderError):
     pass
 
 
-@attr.s(hash=True)
+@dataclass
 class MissingHeader(MissingHeaderError):
-    name = attr.ib()
+    name: str
 
     def __str__(self):
         return "Missing header (without default value): {0}".format(
             self.name)
 
 
-@attr.s(hash=True)
+@dataclass
 class MissingRequiredHeader(MissingHeaderError):
-    name = attr.ib()
+    name: str
 
     def __str__(self):
         return "Missing required header: {0}".format(self.name)
@@ -41,18 +44,18 @@ class MissingParameterError(OpenAPIParameterError):
     pass
 
 
-@attr.s(hash=True)
+@dataclass
 class MissingParameter(MissingParameterError):
-    name = attr.ib()
+    name: str
 
     def __str__(self):
         return "Missing parameter (without default value): {0}".format(
             self.name)
 
 
-@attr.s(hash=True)
+@dataclass
 class MissingRequiredParameter(MissingParameterError):
-    name = attr.ib()
+    name: str
 
     def __str__(self):
         return "Missing required parameter: {0}".format(self.name)
@@ -67,17 +70,17 @@ class MissingRequestBodyError(OpenAPIRequestBodyError):
     pass
 
 
-@attr.s(hash=True)
+@dataclass
 class MissingRequestBody(MissingRequestBodyError):
-    request = attr.ib()
+    request: OpenAPIRequest
 
     def __str__(self):
         return "Missing request body"
 
 
-@attr.s(hash=True)
+@dataclass
 class MissingRequiredRequestBody(MissingRequestBodyError):
-    request = attr.ib()
+    request: OpenAPIRequest
 
     def __str__(self):
         return "Missing required request body"
@@ -87,9 +90,9 @@ class OpenAPIResponseError(OpenAPIError):
     pass
 
 
-@attr.s(hash=True)
+@dataclass
 class MissingResponseContent(OpenAPIResponseError):
-    response = attr.ib()
+    response: OpenAPIResponse
 
     def __str__(self):
         return "Missing response content"
diff --git a/openapi_core/templating/datatypes.py b/openapi_core/templating/datatypes.py
index 0a03d15d..5aa62d49 100644
--- a/openapi_core/templating/datatypes.py
+++ b/openapi_core/templating/datatypes.py
@@ -1,10 +1,12 @@
-import attr
+from typing import Dict, Optional
 
+from dataclasses import dataclass
 
-@attr.s
+
+@dataclass
 class TemplateResult:
-    pattern = attr.ib(default=None)
-    variables = attr.ib(default=None)
+    pattern: Optional[str] = None
+    variables: Optional[Dict] = None
 
     @property
     def resolved(self):
diff --git a/openapi_core/templating/media_types/exceptions.py b/openapi_core/templating/media_types/exceptions.py
index aa1240ca..03c429e1 100644
--- a/openapi_core/templating/media_types/exceptions.py
+++ b/openapi_core/templating/media_types/exceptions.py
@@ -1,4 +1,6 @@
-import attr
+from typing import List
+
+from dataclasses import dataclass
 
 from openapi_core.exceptions import OpenAPIError
 
@@ -7,10 +9,10 @@ class MediaTypeFinderError(OpenAPIError):
     """Media type finder error"""
 
 
-@attr.s(hash=True)
+@dataclass
 class MediaTypeNotFound(MediaTypeFinderError):
-    mimetype = attr.ib()
-    availableMimetypes = attr.ib()
+    mimetype: str
+    availableMimetypes: List[str]
 
     def __str__(self):
         return (
diff --git a/openapi_core/templating/paths/exceptions.py b/openapi_core/templating/paths/exceptions.py
index 0ed2e7e4..615b9f5e 100644
--- a/openapi_core/templating/paths/exceptions.py
+++ b/openapi_core/templating/paths/exceptions.py
@@ -1,4 +1,4 @@
-import attr
+from dataclasses import dataclass
 
 from openapi_core.exceptions import OpenAPIError
 
@@ -7,30 +7,30 @@ class PathError(OpenAPIError):
     """Path error"""
 
 
-@attr.s(hash=True)
+@dataclass
 class PathNotFound(PathError):
     """Find path error"""
-    url = attr.ib()
+    url: str
 
     def __str__(self):
         return "Path not found for {0}".format(self.url)
 
 
-@attr.s(hash=True)
+@dataclass
 class OperationNotFound(PathError):
     """Find path operation error"""
-    url = attr.ib()
-    method = attr.ib()
+    url: str
+    method: str
 
     def __str__(self):
         return "Operation {0} not found for {1}".format(
             self.method, self.url)
 
 
-@attr.s(hash=True)
+@dataclass
 class ServerNotFound(PathError):
     """Find server error"""
-    url = attr.ib()
+    url: str
 
     def __str__(self):
         return "Server not found for {0}".format(self.url)
diff --git a/openapi_core/templating/responses/exceptions.py b/openapi_core/templating/responses/exceptions.py
index 3602ae63..1427efc9 100644
--- a/openapi_core/templating/responses/exceptions.py
+++ b/openapi_core/templating/responses/exceptions.py
@@ -1,4 +1,6 @@
-import attr
+from typing import List
+
+from dataclasses import dataclass
 
 from openapi_core.exceptions import OpenAPIError
 
@@ -7,11 +9,11 @@ class ResponseFinderError(OpenAPIError):
     """Response finder error"""
 
 
-@attr.s(hash=True)
+@dataclass
 class ResponseNotFound(ResponseFinderError):
     """Find response error"""
-    http_status = attr.ib()
-    responses = attr.ib()
+    http_status: int
+    availableresponses: List[str]
 
     def __str__(self):
         return "Unknown response http status: {0}".format(
diff --git a/openapi_core/templating/responses/finders.py b/openapi_core/templating/responses/finders.py
index 6e5532e9..9518fd90 100644
--- a/openapi_core/templating/responses/finders.py
+++ b/openapi_core/templating/responses/finders.py
@@ -16,6 +16,6 @@ def find(self, http_status='default'):
             return self.responses / http_status_range
 
         if 'default' not in self.responses:
-            raise ResponseNotFound(http_status, self.responses)
+            raise ResponseNotFound(http_status, list(self.responses.keys()))
 
         return self.responses / 'default'
diff --git a/openapi_core/testing/requests.py b/openapi_core/testing/requests.py
index fdde9d61..d7af9495 100644
--- a/openapi_core/testing/requests.py
+++ b/openapi_core/testing/requests.py
@@ -1,7 +1,7 @@
 """OpenAPI core testing requests module"""
 from urllib.parse import urljoin
 
-from werkzeug.datastructures import ImmutableMultiDict
+from werkzeug.datastructures import Headers, ImmutableMultiDict
 
 from openapi_core.validation.request.datatypes import (
     RequestParameters, OpenAPIRequest,
@@ -15,13 +15,18 @@ def create(
             cls, host_url, method, path, path_pattern=None, args=None,
             view_args=None, headers=None, cookies=None, data=None,
             mimetype='application/json'):
+        path_pattern = path_pattern or path
+
+        path = view_args or {}
+        query = ImmutableMultiDict(args or {})
+        header = Headers(headers or {})
+        cookie = ImmutableMultiDict(cookies or {})
         parameters = RequestParameters(
-            path=view_args or {},
-            query=ImmutableMultiDict(args or []),
-            header=headers or {},
-            cookie=cookies or {},
+            path=path,
+            query=query,
+            header=header,
+            cookie=cookie,
         )
-        path_pattern = path_pattern or path
         method = method.lower()
         body = data or ''
         full_url_pattern = urljoin(host_url, path_pattern)
diff --git a/openapi_core/testing/responses.py b/openapi_core/testing/responses.py
index 2e19bec6..9eae17eb 100644
--- a/openapi_core/testing/responses.py
+++ b/openapi_core/testing/responses.py
@@ -1,4 +1,6 @@
 """OpenAPI core testing responses module"""
+from werkzeug.datastructures import Headers
+
 from openapi_core.validation.response.datatypes import OpenAPIResponse
 
 
@@ -8,9 +10,10 @@ class MockResponseFactory:
     def create(
             cls, data, status_code=200, headers=None,
             mimetype='application/json'):
+        headers = Headers(headers or {})
         return OpenAPIResponse(
             data=data,
             status_code=status_code,
-            headers=headers or {},
+            headers=headers,
             mimetype=mimetype,
         )
diff --git a/openapi_core/unmarshalling/schemas/exceptions.py b/openapi_core/unmarshalling/schemas/exceptions.py
index 67eede67..20bb63fa 100644
--- a/openapi_core/unmarshalling/schemas/exceptions.py
+++ b/openapi_core/unmarshalling/schemas/exceptions.py
@@ -1,4 +1,6 @@
-import attr
+from typing import List
+
+from dataclasses import dataclass, field
 
 from openapi_core.exceptions import OpenAPIError
 
@@ -18,11 +20,11 @@ class UnmarshallerError(UnmarshalError):
     pass
 
 
-@attr.s(hash=True)
+@dataclass
 class InvalidSchemaValue(ValidateError):
-    value = attr.ib()
-    type = attr.ib()
-    schema_errors = attr.ib(factory=tuple)
+    value: str
+    type: str
+    schema_errors: List[Exception] = field(default_factory=list)
 
     def __str__(self):
         return (
@@ -30,12 +32,12 @@ def __str__(self):
         ).format(value=self.value, type=self.type, errors=self.schema_errors)
 
 
-@attr.s(hash=True)
+@dataclass
 class InvalidSchemaFormatValue(UnmarshallerError):
     """Value failed to format with formatter"""
-    value = attr.ib()
-    type = attr.ib()
-    original_exception = attr.ib()
+    value: str
+    type: str
+    original_exception: Exception
 
     def __str__(self):
         return (
@@ -46,10 +48,10 @@ def __str__(self):
         )
 
 
-@attr.s(hash=True)
+@dataclass
 class FormatterNotFoundError(UnmarshallerError):
     """Formatter not found to unmarshal"""
-    type_format = attr.ib()
+    type_format: str
 
     def __str__(self):
         return "Formatter not found for {format} format".format(
diff --git a/openapi_core/validation/datatypes.py b/openapi_core/validation/datatypes.py
index a5434c25..1eb58b9d 100644
--- a/openapi_core/validation/datatypes.py
+++ b/openapi_core/validation/datatypes.py
@@ -1,10 +1,12 @@
 """OpenAPI core validation datatypes module"""
-import attr
+from typing import List
 
+from dataclasses import dataclass
 
-@attr.s
+
+@dataclass
 class BaseValidationResult:
-    errors = attr.ib(factory=list)
+    errors: List[Exception]
 
     def raise_for_errors(self):
         for error in self.errors:
diff --git a/openapi_core/validation/exceptions.py b/openapi_core/validation/exceptions.py
index 1791fa0e..004068f1 100644
--- a/openapi_core/validation/exceptions.py
+++ b/openapi_core/validation/exceptions.py
@@ -1,5 +1,5 @@
 """OpenAPI core validation exceptions module"""
-import attr
+from dataclasses import dataclass
 
 from openapi_core.exceptions import OpenAPIError
 
@@ -8,7 +8,7 @@ class ValidationError(OpenAPIError):
     pass
 
 
-@attr.s(hash=True)
+@dataclass
 class InvalidSecurity(ValidationError):
 
     def __str__(self):
diff --git a/openapi_core/validation/request/datatypes.py b/openapi_core/validation/request/datatypes.py
index 9c0a07b8..f93feb0f 100644
--- a/openapi_core/validation/request/datatypes.py
+++ b/openapi_core/validation/request/datatypes.py
@@ -1,11 +1,13 @@
 """OpenAPI core validation request datatypes module"""
-import attr
+from typing import Dict, Optional
+
+from dataclasses import dataclass, field
 from werkzeug.datastructures import ImmutableMultiDict, Headers
 
 from openapi_core.validation.datatypes import BaseValidationResult
 
 
-@attr.s
+@dataclass
 class RequestParameters:
     """OpenAPI request parameters dataclass.
 
@@ -15,20 +17,20 @@ class RequestParameters:
         header
             Request headers as Headers.
         cookie
-            Request cookies as dict.
+            Request cookies as MultiDict.
         path
             Path parameters as dict. Gets resolved against spec if empty.
     """
-    query = attr.ib(factory=ImmutableMultiDict)
-    header = attr.ib(factory=Headers, converter=Headers)
-    cookie = attr.ib(factory=dict)
-    path = attr.ib(factory=dict)
+    query: ImmutableMultiDict = field(default_factory=ImmutableMultiDict)
+    header: Headers = field(default_factory=Headers)
+    cookie: ImmutableMultiDict = field(default_factory=ImmutableMultiDict)
+    path: Dict = field(default_factory=dict)
 
     def __getitem__(self, location):
         return getattr(self, location)
 
 
-@attr.s
+@dataclass
 class OpenAPIRequest:
     """OpenAPI request dataclass.
 
@@ -51,18 +53,15 @@ class OpenAPIRequest:
             the mimetype would be "text/html".
     """
 
-    full_url_pattern = attr.ib()
-    method = attr.ib()
-    body = attr.ib()
-    mimetype = attr.ib()
-    parameters = attr.ib(factory=RequestParameters)
+    full_url_pattern: str
+    method: str
+    body: str
+    mimetype: str
+    parameters: RequestParameters = field(default_factory=RequestParameters)
 
 
-@attr.s
+@dataclass
 class RequestValidationResult(BaseValidationResult):
-    body = attr.ib(default=None)
-    parameters = attr.ib(factory=RequestParameters)
-    security = attr.ib(default=None)
-    server = attr.ib(default=None)
-    path = attr.ib(default=None)
-    operation = attr.ib(default=None)
+    body: Optional[str] = None
+    parameters: RequestParameters = field(default_factory=RequestParameters)
+    security: Optional[Dict[str, str]] = None
diff --git a/openapi_core/validation/response/datatypes.py b/openapi_core/validation/response/datatypes.py
index ea58a0c7..3fa06fa2 100644
--- a/openapi_core/validation/response/datatypes.py
+++ b/openapi_core/validation/response/datatypes.py
@@ -1,11 +1,12 @@
 """OpenAPI core validation response datatypes module"""
-import attr
+from typing import Dict, Optional
+from dataclasses import dataclass, field
 from werkzeug.datastructures import Headers
 
 from openapi_core.validation.datatypes import BaseValidationResult
 
 
-@attr.s
+@dataclass
 class OpenAPIResponse:
     """OpenAPI request dataclass.
 
@@ -19,13 +20,13 @@ class OpenAPIResponse:
         mimetype
             Lowercase content type without charset.
     """
-    data = attr.ib()
-    status_code = attr.ib()
-    mimetype = attr.ib()
-    headers = attr.ib(factory=Headers, converter=Headers)
+    data: str
+    status_code: int
+    mimetype: str
+    headers: Headers = field(default_factory=Headers)
 
 
-@attr.s
+@dataclass
 class ResponseValidationResult(BaseValidationResult):
-    data = attr.ib(default=None)
-    headers = attr.ib(factory=dict)
+    data: Optional[str] = None
+    headers: Dict = field(default_factory=dict)
diff --git a/requirements.txt b/requirements.txt
index 75a2cf77..3542d48a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,6 +2,6 @@ isodate==0.6.0
 dictpath==0.1.3
 openapi-spec-validator
 openapi-schema-validator
-attrs
 parse==1.14.0
 more-itertools>=5.0.0
+dataclasses==0.8; python_version=="3.6"
diff --git a/setup.cfg b/setup.cfg
index 67f4cc8b..7de244ae 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -29,10 +29,10 @@ install_requires =
     dictpath
     openapi-spec-validator
     openapi-schema-validator
-    attrs
     werkzeug
     parse
     more-itertools
+    dataclasses; python_version=="3.6"
 tests_require =
     pytest>=5.0.0
     pytest-flake8
diff --git a/tests/integration/contrib/flask/test_flask_requests.py b/tests/integration/contrib/flask/test_flask_requests.py
index 5de5070f..64d3f8cc 100644
--- a/tests/integration/contrib/flask/test_flask_requests.py
+++ b/tests/integration/contrib/flask/test_flask_requests.py
@@ -1,6 +1,6 @@
 from urllib.parse import urljoin
 
-from werkzeug.datastructures import EnvironHeaders, ImmutableMultiDict
+from werkzeug.datastructures import Headers, ImmutableMultiDict
 
 from openapi_core.contrib.flask import FlaskOpenAPIRequest
 from openapi_core.validation.request.datatypes import RequestParameters
@@ -15,7 +15,7 @@ def test_simple(self, request_factory, request):
 
         path = {}
         query = ImmutableMultiDict([])
-        headers = EnvironHeaders(request.environ)
+        headers = Headers(request.headers)
         cookies = {}
         assert openapi_request.parameters == RequestParameters(
             path=path,
@@ -39,7 +39,7 @@ def test_multiple_values(self, request_factory, request):
         query = ImmutableMultiDict([
             ('a', 'b'), ('a', 'c'),
         ])
-        headers = EnvironHeaders(request.environ)
+        headers = Headers(request.headers)
         cookies = {}
         assert openapi_request.parameters == RequestParameters(
             path=path,
@@ -60,7 +60,7 @@ def test_url_rule(self, request_factory, request):
 
         path = {'id': 12}
         query = ImmutableMultiDict([])
-        headers = EnvironHeaders(request.environ)
+        headers = Headers(request.headers)
         cookies = {}
         assert openapi_request.parameters == RequestParameters(
             path=path,
diff --git a/tests/integration/contrib/requests/test_requests_requests.py b/tests/integration/contrib/requests/test_requests_requests.py
index 2ea214e3..d6f92d43 100644
--- a/tests/integration/contrib/requests/test_requests_requests.py
+++ b/tests/integration/contrib/requests/test_requests_requests.py
@@ -4,6 +4,9 @@
 from openapi_core.validation.request.datatypes import RequestParameters
 
 
+from werkzeug.datastructures import Headers
+
+
 class TestRequestsOpenAPIRequest:
 
     def test_simple(self, request_factory, request):
@@ -13,7 +16,7 @@ def test_simple(self, request_factory, request):
 
         path = {}
         query = ImmutableMultiDict([])
-        headers = request.headers
+        headers = Headers(dict(request.headers))
         cookies = {}
         prepared = request.prepare()
         assert openapi_request.parameters == RequestParameters(
@@ -37,7 +40,7 @@ def test_multiple_values(self, request_factory, request):
         query = ImmutableMultiDict([
             ('a', 'b'), ('a', 'c'),
         ])
-        headers = request.headers
+        headers = Headers(dict(request.headers))
         cookies = {}
         assert openapi_request.parameters == RequestParameters(
             path=path,
@@ -59,9 +62,9 @@ def test_url_rule(self, request_factory, request):
         # empty when not bound to spec
         path = {}
         query = ImmutableMultiDict([])
-        headers = (
-            ('Content-Type', 'application/json'),
-        )
+        headers = Headers({
+            'Content-Type': 'application/json',
+        })
         cookies = {}
         assert openapi_request.parameters == RequestParameters(
             path=path,
diff --git a/tests/integration/contrib/test_django.py b/tests/integration/contrib/test_django.py
index 76bf5f84..55e5d443 100644
--- a/tests/integration/contrib/test_django.py
+++ b/tests/integration/contrib/test_django.py
@@ -1,6 +1,7 @@
 import sys
 
 import pytest
+from werkzeug.datastructures import Headers
 
 from openapi_core.contrib.django import (
     DjangoOpenAPIRequest, DjangoOpenAPIResponse,
@@ -71,9 +72,9 @@ def test_no_resolver(self, request_factory):
 
         path = {}
         query = {}
-        headers = {
+        headers = Headers({
             'Cookie': '',
-        }
+        })
         cookies = {}
         assert openapi_request.parameters == RequestParameters(
             path=path,
@@ -96,9 +97,9 @@ def test_simple(self, request_factory):
 
         path = {}
         query = {}
-        headers = {
+        headers = Headers({
             'Cookie': '',
-        }
+        })
         cookies = {}
         assert openapi_request.parameters == RequestParameters(
             path=path,
@@ -123,9 +124,9 @@ def test_url_rule(self, request_factory):
             'object_id': '1',
         }
         query = {}
-        headers = {
+        headers = Headers({
             'Cookie': '',
-        }
+        })
         cookies = {}
         assert openapi_request.parameters == RequestParameters(
             path=path,
@@ -148,9 +149,9 @@ def test_url_regexp_pattern(self, request_factory):
 
         path = {}
         query = {}
-        headers = {
+        headers = Headers({
             'Cookie': '',
-        }
+        })
         cookies = {}
         assert openapi_request.parameters == RequestParameters(
             path=path,