diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index de794382..b3a6fdd2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -42,6 +42,9 @@ jobs:
           - "3.10"
         os:
           - ubuntu-latest
+        extension:
+          - "skip_cython"
+          - "use_cython"
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3
@@ -55,7 +58,12 @@ jobs:
           python-version: ${{ matrix.python-version }}
           cache: "poetry"
       - name: Install Dependencies
-        run: poetry install
+        run: |
+          if [ "${{ matrix.extension }}" = "skip_cython" ]; then
+            SKIP_CYTHON=1 poetry install
+          else:
+            poetry install
+          fi
       - name: Test with Pytest
         run: export $(dbus-launch); poetry run pytest --cov-report=xml
       - name: Upload coverage to Codecov
diff --git a/build.py b/build.py
index 058be070..4eca0540 100644
--- a/build.py
+++ b/build.py
@@ -1,6 +1,7 @@
 """Build optional cython modules."""
 
 import contextlib
+import os
 from distutils.command.build_ext import build_ext
 
 
@@ -13,6 +14,8 @@ def build_extensions(self):
 
 
 def build(setup_kwargs):
+    if os.environ.get("SKIP_CYTHON", False):
+        return
     with contextlib.suppress(Exception):
         from Cython.Build import cythonize
 
diff --git a/src/dbus_fast/_private/marshaller.py b/src/dbus_fast/_private/marshaller.py
index e55de9ec..30ffd1e0 100644
--- a/src/dbus_fast/_private/marshaller.py
+++ b/src/dbus_fast/_private/marshaller.py
@@ -9,7 +9,7 @@
 class Marshaller:
     """Marshall data for Dbus."""
 
-    __slots__ = ("signature_tree", "buffer", "body")
+    __slots__ = ("signature_tree", "_buf", "body")
 
     def __init__(self, signature: str, body: List[Any]) -> None:
         """Marshaller constructor."""