diff --git a/pyproject.toml b/pyproject.toml
index 8638c570..3212111b 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -53,7 +53,7 @@ tornado = ["tornado>=6.5.0"]
 gthread = []
 setproctitle = ["setproctitle"]
 http2 = ["h2>=4.1.0"]
-fast = ["gunicorn_h1c>=0.6.3"]
+fast = ["gunicorn_h1c>=0.6.4"]
 testing = [
     "gevent>=24.10.1",
     "eventlet>=0.40.3",
diff --git a/requirements_test.txt b/requirements_test.txt
index 4d26756a..40e28207 100644
--- a/requirements_test.txt
+++ b/requirements_test.txt
@@ -3,4 +3,4 @@ coverage
 pytest>=7.2.0
 pytest-cov
 pytest-asyncio
-gunicorn_h1c>=0.6.2
+gunicorn_h1c>=0.6.4
diff --git a/tests/conftest.py b/tests/conftest.py
index c3824279..f1668590 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -20,6 +20,10 @@ if tests_dir not in sys.path:
 def http_parser(request):
     """Parametrize tests over http_parser implementations."""
     if request.param == "fast":
+        # gunicorn_h1c ships as a CPython C extension; it is not reliable
+        # under PyPy (SIGSEGV observed in CI). Skip the fast parameter there.
+        if hasattr(sys, "pypy_version_info"):
+            pytest.skip("gunicorn_h1c not supported on PyPy")
         gunicorn_h1c = pytest.importorskip("gunicorn_h1c", reason="gunicorn_h1c required")
         # Require >= 0.6.2 for asgi_headers support
         if not hasattr(gunicorn_h1c.H1CProtocol, 'asgi_headers'):
diff --git a/tests/requests/invalid/rfc9110_field_value_ctl_bel_01.py b/tests/requests/invalid/rfc9110_field_value_ctl_bel_01.py
index 4203cfe9..abf559d9 100644
--- a/tests/requests/invalid/rfc9110_field_value_ctl_bel_01.py
+++ b/tests/requests/invalid/rfc9110_field_value_ctl_bel_01.py
@@ -7,4 +7,3 @@
 # appear, to prevent log/response injection and parser confusion.
 from gunicorn.http.errors import InvalidHeader
 request = InvalidHeader
-python_only = True
diff --git a/tests/requests/invalid/rfc9110_field_value_ctl_del_01.py b/tests/requests/invalid/rfc9110_field_value_ctl_del_01.py
index cd6cd1aa..f992575c 100644
--- a/tests/requests/invalid/rfc9110_field_value_ctl_del_01.py
+++ b/tests/requests/invalid/rfc9110_field_value_ctl_del_01.py
@@ -6,4 +6,3 @@
 # it must not appear in a field-value.
 from gunicorn.http.errors import InvalidHeader
 request = InvalidHeader
-python_only = True
diff --git a/tests/requests/invalid/rfc9110_trailer_forbidden_cl_01.py b/tests/requests/invalid/rfc9110_trailer_forbidden_cl_01.py
index b0f8ccae..05bdea9c 100644
--- a/tests/requests/invalid/rfc9110_trailer_forbidden_cl_01.py
+++ b/tests/requests/invalid/rfc9110_trailer_forbidden_cl_01.py
@@ -6,4 +6,3 @@
 # smuggling vector; origin must reject.
 from gunicorn.http.errors import InvalidHeaderName
 request = InvalidHeaderName
-python_only = True
diff --git a/tests/requests/invalid/rfc9110_trailer_forbidden_host_01.py b/tests/requests/invalid/rfc9110_trailer_forbidden_host_01.py
index fe897329..3d747dea 100644
--- a/tests/requests/invalid/rfc9110_trailer_forbidden_host_01.py
+++ b/tests/requests/invalid/rfc9110_trailer_forbidden_host_01.py
@@ -7,5 +7,3 @@
 # Content-Length, Transfer-Encoding). Accepting them enables smuggling.
 from gunicorn.http.errors import InvalidHeaderName
 request = InvalidHeaderName
-# The C parser (gunicorn_h1c) does not yet enforce this rule.
-python_only = True
diff --git a/tests/requests/invalid/rfc9110_trailer_forbidden_te_01.py b/tests/requests/invalid/rfc9110_trailer_forbidden_te_01.py
index caa2f5ac..d2c4c471 100644
--- a/tests/requests/invalid/rfc9110_trailer_forbidden_te_01.py
+++ b/tests/requests/invalid/rfc9110_trailer_forbidden_te_01.py
@@ -6,4 +6,3 @@
 # and must not be accepted.
 from gunicorn.http.errors import InvalidHeaderName
 request = InvalidHeaderName
-python_only = True
diff --git a/tests/requests/invalid/rfc9112_target_asterisk_non_options_01.py b/tests/requests/invalid/rfc9112_target_asterisk_non_options_01.py
index cd5bfe62..a3616620 100644
--- a/tests/requests/invalid/rfc9112_target_asterisk_non_options_01.py
+++ b/tests/requests/invalid/rfc9112_target_asterisk_non_options_01.py
@@ -7,5 +7,3 @@
 # rejected as an ill-formed request-line.
 from gunicorn.http.errors import InvalidRequestLine
 request = InvalidRequestLine
-# The C parser (gunicorn_h1c) does not yet enforce this rule.
-python_only = True
diff --git a/tests/requests/invalid/rfc9112_target_authority_non_connect_01.py b/tests/requests/invalid/rfc9112_target_authority_non_connect_01.py
index 2a91f311..85bfb56a 100644
--- a/tests/requests/invalid/rfc9112_target_authority_non_connect_01.py
+++ b/tests/requests/invalid/rfc9112_target_authority_non_connect_01.py
@@ -6,5 +6,3 @@
 # the CONNECT method. Any other method carrying it must be rejected.
 from gunicorn.http.errors import InvalidRequestLine
 request = InvalidRequestLine
-# The C parser (gunicorn_h1c) does not yet enforce this rule.
-python_only = True
diff --git a/tests/requests/invalid/rfc9112_target_relative_01.py b/tests/requests/invalid/rfc9112_target_relative_01.py
index ea6bb9e2..8dd816d2 100644
--- a/tests/requests/invalid/rfc9112_target_relative_01.py
+++ b/tests/requests/invalid/rfc9112_target_relative_01.py
@@ -7,5 +7,3 @@
 # like "foo/bar" matches none of these and must be rejected.
 from gunicorn.http.errors import InvalidRequestLine
 request = InvalidRequestLine
-# The C parser (gunicorn_h1c) does not yet enforce this rule.
-python_only = True