diff --git a/CONTRIBUTE.rst b/CONTRIBUTE.rst
index 8063c8b230b86ed2253fad9bcf26b2b9eb953b89..978d5fd3c4149a89cf5b6ba0a6d7a8d0237a7daf 100644
--- a/CONTRIBUTE.rst
+++ b/CONTRIBUTE.rst
@@ -75,13 +75,10 @@ A useful trick for working on the source code is to build in-place so that there
 is no need to re-install after each change.  This can be done with the following
 command ::
 
-    python setup.py build_ext -i --cython
+    python setup.py build_ext -i
 
 The ``kwant`` subdirectory of the source distribution will be thus turned into
 a proper Python package that can be imported.  To be able to import Kwant from
 within Python, one can either work in the root directory of the distribution
 (where the subdirectory ``kwant`` is located), or make a (symbolic) link from
 somewhere in the Python search path to the the package subdirectory.
-
-The option ``--cython`` enables the translation of .pyx files into .c files.
-It is only needed if any .pyx files have been modified.
diff --git a/setup.py b/setup.py
index cb9158a333ac4206046c19e2b6ad364959f7664d..3b884b97e239eedb01950de25217d13d3deb39f4 100755
--- a/setup.py
+++ b/setup.py
@@ -62,7 +62,7 @@ try:
     sys.argv.remove(CYTHON_OPTION)
     use_cython = True
 except ValueError:
-    use_cython = False
+    use_cython = version_is_from_git
 
 if use_cython:
     try: