diff --git a/.gitmodules b/.gitmodules
index 1e901ef79f2..6edb2eea5b2 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,4 +1,4 @@
 [submodule "vendor/llhttp"]
     path = vendor/llhttp
     url = https://github.com/nodejs/llhttp.git
-    branch = v8.1.1
+    branch = v8.x
diff --git a/docs/contributing.rst b/docs/contributing.rst
index 10a4a4bc2d7..b1dfdf01139 100644
--- a/docs/contributing.rst
+++ b/docs/contributing.rst
@@ -110,6 +110,8 @@ Install pre-commit hooks:
 
 Congratulations, you are ready to run the test suite!
 
+.. include:: ../vendor/README.rst
+
 
 Run autoformatter
 -----------------
diff --git a/tests/test_http_parser.py b/tests/test_http_parser.py
index cc30629dd0d..950c243ef6b 100644
--- a/tests/test_http_parser.py
+++ b/tests/test_http_parser.py
@@ -685,6 +685,7 @@ def test_http_response_parser_bad(response) -> None:
         response.feed_data(b"HTT/1\r\n\r\n")
 
 
+@pytest.mark.skipif(not NO_EXTENSIONS, reason="Behaviour has changed in C parser")
 def test_http_response_parser_code_under_100(response) -> None:
     msg = response.feed_data(b"HTTP/1.1 99 test\r\n\r\n")[0][0][0]
     assert msg.code == 99
diff --git a/vendor/README.rst b/vendor/README.rst
new file mode 100644
index 00000000000..1f10e20cce2
--- /dev/null
+++ b/vendor/README.rst
@@ -0,0 +1,23 @@
+LLHTTP
+------
+
+When building aiohttp from source, there is a pure Python parser used by default.
+For better performance, you may want to build the higher performance C parser.
+
+To build this ``llhttp`` parser, first get/update the submodules (to update to a
+newer release, add ``--remote`` and check the branch in ``.gitmodules``)::
+
+    git submodule update --init --recursive
+
+Then build ``llhttp``::
+
+    cd vendor/llhttp/
+    npm install
+    make
+
+Then build our parser::
+
+    cd -
+    make cythonize
+
+Then you can build or install it with ``python -m build`` or ``pip install -e .``
diff --git a/vendor/llhttp b/vendor/llhttp
index 69d6db20085..7e18596bae8 160000
--- a/vendor/llhttp
+++ b/vendor/llhttp
@@ -1 +1 @@
-Subproject commit 69d6db2008508489d19267a0dcab30602b16fc5b
+Subproject commit 7e18596bae8f63692ded9d3250d5d984fe90dcfb