diff --git a/.github/workflows/integration.yml b/.github/workflows/integration.yml
index f5e8f619..6041c36f 100644
--- a/.github/workflows/integration.yml
+++ b/.github/workflows/integration.yml
@@ -19,11 +19,10 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        stack_version: ['7.10.2']
         cluster: ["opendistro", "opensearch"]
 
     steps:
       - name: Checkout
         uses: actions/checkout@v2
       - run: "./.ci/run-tests ${{ matrix.cluster }} "
-        name: Integ ${{ matrix.stack_version }} ${{ matrix.cluster }}
+        name: Integ ${{ matrix.cluster }}
diff --git a/.github/workflows/unified-release.yml b/.github/workflows/unified-release.yml
index dd3c2aaf..67c86dc3 100644
--- a/.github/workflows/unified-release.yml
+++ b/.github/workflows/unified-release.yml
@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        stack_version: ['7.10.2']
+        stack_version: ['1.0.0']
 
     steps:
       - name: Checkout
diff --git a/opensearch/_version.py b/opensearch/_version.py
index 39a87dc8..7fd3764d 100644
--- a/opensearch/_version.py
+++ b/opensearch/_version.py
@@ -24,4 +24,4 @@
 #  specific language governing permissions and limitations
 #  under the License.
 
-__versionstr__ = "7.10.2"
+__versionstr__ = "1.0.0"
diff --git a/opensearch/connection/base.py b/opensearch/connection/base.py
index 2a70e2d5..05d81c71 100644
--- a/opensearch/connection/base.py
+++ b/opensearch/connection/base.py
@@ -28,7 +28,6 @@ import binascii
 import gzip
 import io
 import logging
-import os
 import re
 import warnings
 from platform import python_version
@@ -38,7 +37,7 @@ try:
 except ImportError:
     import json
 
-from .. import __version__, __versionstr__
+from .. import __versionstr__
 from ..exceptions import (
     HTTP_EXCEPTIONS,
     ImproperlyConfigured,
@@ -128,13 +127,6 @@ class Connection(object):
         if opaque_id:
             self.headers["x-opaque-id"] = opaque_id
 
-        if os.getenv("ELASTIC_CLIENT_APIVERSIONING") == "1":
-            self.headers.setdefault(
-                "accept",
-                "application/vnd.opensearch+json;compatible-with=%s"
-                % (str(__version__[0]),),
-            )
-
         self.headers.setdefault("content-type", "application/json")
         self.headers.setdefault("user-agent", self._get_default_user_agent())
 
diff --git a/opensearch/serializer.py b/opensearch/serializer.py
index 2f42798d..fcc9b146 100644
--- a/opensearch/serializer.py
+++ b/opensearch/serializer.py
@@ -163,12 +163,8 @@ class Deserializer(object):
         if not mimetype:
             deserializer = self.default
         else:
-            # split out 'charset' and 'compatible-width' options
-            mimetype = mimetype.partition(";")[0].strip()
-            # Treat 'application/vnd.opensearch+json'
-            # as application/json for compatibility.
-            if mimetype == "application/vnd.opensearch+json":
-                mimetype = "application/json"
+            # split out charset
+            mimetype, _, _ = mimetype.partition(";")
             try:
                 deserializer = self.serializers[mimetype]
             except KeyError:
diff --git a/test_opensearch/test_connection.py b/test_opensearch/test_connection.py
index 9659f124..c02a7183 100644
--- a/test_opensearch/test_connection.py
+++ b/test_opensearch/test_connection.py
@@ -28,7 +28,6 @@
 import gzip
 import io
 import json
-import os
 import re
 import ssl
 import warnings
@@ -174,26 +173,6 @@ class TestBaseConnection(TestCase):
             conn = Connection(**kwargs)
             assert conn.host == expected_host
 
-    def test_compatibility_accept_header(self):
-        try:
-            conn = Connection()
-            assert "accept" not in conn.headers
-
-            os.environ["ELASTIC_CLIENT_APIVERSIONING"] = "0"
-
-            conn = Connection()
-            assert "accept" not in conn.headers
-
-            os.environ["ELASTIC_CLIENT_APIVERSIONING"] = "1"
-
-            conn = Connection()
-            assert (
-                conn.headers["accept"]
-                == "application/vnd.opensearch+json;compatible-with=7"
-            )
-        finally:
-            os.environ.pop("ELASTIC_CLIENT_APIVERSIONING")
-
 
 class TestUrllib3Connection(TestCase):
     def _get_mock_connection(self, connection_params={}, response_body=b"{}"):
diff --git a/test_opensearch/test_serializer.py b/test_opensearch/test_serializer.py
index b92ab3f3..aa7d2c25 100644
--- a/test_opensearch/test_serializer.py
+++ b/test_opensearch/test_serializer.py
@@ -226,17 +226,6 @@ class TestDeserializer(TestCase):
             self.de.loads('{"some":"data"}', "text/plain; charset=whatever"),
         )
 
-    def test_deserialize_compatibility_header(self):
-        for content_type in (
-            "application/vnd.opensearch+json;compatible-with=7",
-            "application/vnd.opensearch+json; compatible-with=7",
-            "application/vnd.opensearch+json;compatible-with=8",
-            "application/vnd.opensearch+json; compatible-with=8",
-        ):
-            self.assertEqual(
-                {"some": "data"}, self.de.loads('{"some":"data"}', content_type)
-            )
-
     def test_raises_serialization_error_on_unknown_mimetype(self):
         self.assertRaises(SerializationError, self.de.loads, "{}", "text/html")