diff --git a/pkgs/development/python-modules/pycapnp/default.nix b/pkgs/development/python-modules/pycapnp/default.nix
index 51f36bd86eec..f06b010a5467 100644
--- a/pkgs/development/python-modules/pycapnp/default.nix
+++ b/pkgs/development/python-modules/pycapnp/default.nix
@@ -1,42 +1,76 @@
 {
   lib,
   buildPythonPackage,
-  capnproto,
-  cython_0,
+  replaceVars,
   fetchFromGitHub,
-  isPy27,
-  isPyPy,
+  fetchpatch2,
+  setuptools,
+  wheel,
+  capnproto,
+  cython,
   pkgconfig,
+  pytest-asyncio,
+  pytestCheckHook,
 }:
 
 buildPythonPackage rec {
   pname = "pycapnp";
   version = "2.0.0";
-  format = "setuptools";
-  disabled = isPyPy || isPy27;
+  format = "pyproject";
 
   src = fetchFromGitHub {
     owner = "capnproto";
     repo = "pycapnp";
     tag = "v${version}";
-    sha256 = "sha256-SVeBRJMMR1Z8+S+QoiUKGRFGUPS/MlmWLi1qRcGcPoE=";
+    hash = "sha256-SVeBRJMMR1Z8+S+QoiUKGRFGUPS/MlmWLi1qRcGcPoE=";
   };
 
-  nativeBuildInputs = [
-    cython_0
+  patches = [
+    # pycapnp hardcodes /usr/include and /usr/local/include as the paths to search
+    # for capnproto's built-in schemas in; replace them with the path to our copy of
+    # capnproto.
+    #
+    # Theoretically, this mechanism could also be used to load capnproto schemas
+    # exposed by other packages (e.g. capnproto-java), which we could support using
+    # a setup hook; but in practice nobody seems to use this mechanism for anything
+    # other than the builtin schemas (based on quick GitHub code search), so I don't
+    # think it's worthwhile.
+    (replaceVars ./include-paths.patch { inherit capnproto; })
+    (fetchpatch2 {
+      name = "cython-3.patch";
+      url = "https://github.com/capnproto/pycapnp/pull/334.diff?full_index=1";
+      hash = "sha256-we7v4RaL7c1tePWl+oYfzMHAfnvnpdMkQgVu9YLwC6Y=";
+    })
+  ];
+
+  build-system = [
+    setuptools
+    wheel
+    cython
     pkgconfig
   ];
 
   buildInputs = [ capnproto ];
 
-  # Tests depend on schema_capnp which fails to generate
-  doCheck = false;
+  nativeCheckInputs = [
+    pytest-asyncio
+    pytestCheckHook
+  ];
+  __darwinAllowLocalNetworking = true;
+  # https://github.com/NixOS/nixpkgs/issues/255262
+  preCheck = ''
+    enabledTestPaths=$PWD/test
+    pushd "$out"
+  '';
+  postCheck = ''
+    popd
+  '';
 
-  pythonImportsCheck = [ "capnp" ];
-
-  meta = with lib; {
+  meta = {
+    description = "Cython wrapping of the C++ Cap'n Proto library";
     homepage = "https://capnproto.github.io/pycapnp/";
-    maintainers = [ ];
-    license = licenses.bsd2;
+    changelog = "https://github.com/capnproto/pycapnp/blob/${src.rev}/CHANGELOG.md";
+    license = lib.licenses.bsd2;
+    maintainers = with lib.maintainers; [ Liamolucko ];
   };
 }
diff --git a/pkgs/development/python-modules/pycapnp/include-paths.patch b/pkgs/development/python-modules/pycapnp/include-paths.patch
new file mode 100644
index 000000000000..04bd7a79e5c2
--- /dev/null
+++ b/pkgs/development/python-modules/pycapnp/include-paths.patch
@@ -0,0 +1,14 @@
+--- a/capnp/lib/capnp.pyx
++++ b/capnp/lib/capnp.pyx
+@@ -4410,10 +4410,7 @@ def load(file_name, display_name=None, imports=[]):
+ # Automatically include the system and built-in capnp paths
+ # Highest priority at position 0
+ _capnp_paths = [
+-    # Common macOS brew location
+-    '/usr/local/include',
+-    # Common posix location
+-    '/usr/include',
++    '@capnproto@/include',
+ ]
+ 
+ class _Loader: