diff --git a/README.md b/README.md
index 48fce71..b5a878d 100644
--- a/README.md
+++ b/README.md
@@ -103,6 +103,8 @@ cd PyRFC
 python -m pip install .
 # or
 python -m build --wheel --sdist --outdir dist
+# or
+PYRFC_BUILD_CYTHON=yes python -m build --wheel --sdist --outdir dist
 pip install --upgrade --no-index --find-links=dist pyrfc
 ```
 
diff --git a/setup.py b/setup.py
index d530948..ee5fd2b 100644
--- a/setup.py
+++ b/setup.py
@@ -11,7 +11,7 @@
 PACKAGE_NAME = "pyrfc"
 MODULE_NAME = "_cyrfc"
 
-build_cython = sys.platform.startswith("linux")
+build_cython = sys.platform.startswith("linux") or bool(os.environ.get("PYRFC_BUILD_CYTHON"))
 
 # build from source on Linux
 CMDCLASS = {}
diff --git a/tox.ini b/tox.ini
index 8a4a4ff..3209004 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,15 +4,16 @@ minversion = 4.5
 envlist =
      format, lint, docs, reuse, sdist, pack,
      py38, py39, py310, py311
+package = wheel
 skip_missing_interpreters = false
 isolated_build = true
 
 [testenv:.pkg]
-passenv = SAPNWRFC_HOME
+passenv = SAPNWRFC_HOME, PYRFC_BUILD_CYTHON
 
 [testenv]
 description = Build binary wheels and run unit tests
-passenv = SAPNWRFC_HOME
+passenv = SAPNWRFC_HOME, PYRFC_BUILD_CYTHON
 deps =
     build
     Cython
@@ -24,12 +25,13 @@ commands =
     python -m build --wheel --outdir dist
     # unit test
     python -m pytest tests --testdox --html-report=./report {posargs}
+    # python -c "import pyrfc; print(pyrfc.__version__)"
 
 [testenv:sdist]
 description = Build sdist
 platform = linux
 skip_install = true
-passenv = SAPNWRFC_HOME
+passenv = SAPNWRFC_HOME, PYRFC_BUILD_CYTHON
 deps =
     Cython
     build
@@ -47,7 +49,8 @@ deps = sphinx
 commands =
     sphinx-build -b html -a -E -d {envtmpdir}/doctrees . {envtmpdir}/html
     # git checkout gh-pages
-    # yes | cp -Rf {env_tmp_dir}/html/. .
+    # yes | cp -Rf {envtmpdir}/html/. .
+
 
 [testenv:format]
 description = Run formatter
@@ -102,7 +105,7 @@ commands =
 description = Build the test package, a prep for unit tests
 platform = darwin
 skip_install = true
-passenv = SAPNWRFC_HOME
+passenv = SAPNWRFC_HOME, PYRFC_BUILD_CYTHON
 allowlist_externals =
     find
     tar