diff --git a/.travis.yml b/.travis.yml
index b30fc28..1c4f5ab 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,10 +1,27 @@
 sudo: required
-dist: xenial
+language: python
+
+matrix:
+    include:
+        - python: "3.4"
+          os: linux
+          dist: trusty
+        - python: "3.5"
+          os: linux
+          dist: xenial
+        - python: "3.6"
+          os: linux
+          dist: bionic
+        - python: "3.7"
+          os: linux
+          dist: bionic
+        - python: "3.8"
+          os: linux
+          dist: focal
+        - python: "3.9-dev"
+          os: linux
+          dist: focal
 
-language:
-    - python
-python:
-    - "3.6"
 addons:
   apt:
     packages:
diff --git a/Changes.rst b/Changes.rst
index 3555586..4e38185 100644
--- a/Changes.rst
+++ b/Changes.rst
@@ -11,7 +11,7 @@ module instead.
 Release 1.3.7 (2020-10-04)
 ==========================
 
-* Rebuild with Cython 0.29.21 for Python 3.8 compatibility.
+* Rebuild with Cython 0.29.21 for Python 3.9 compatibility.
 
 Release 1.3.6 (2019-02-14)
 ==========================
diff --git a/rst/install.rst b/rst/install.rst
index b7ca4f1..f1d656e 100644
--- a/rst/install.rst
+++ b/rst/install.rst
@@ -62,7 +62,7 @@ Development Version
 
 If you have checked out the unstable development version from the
 repository, a bit more effort is required. You need to also have
-Cython_ (0.24 or newer) and Sphinx_ (1.1 or newer) installed, and the
+Cython_ (0.29.21 or newer) and Sphinx_ (1.1 or newer) installed, and the
 necessary commands are::
 
   python setup.py build_cython
diff --git a/setup.cfg b/setup.cfg
index e053fef..a3f8b20 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,7 +1,3 @@
-[sdist]
-formats=bztar
-
 [build_sphinx]
 source-dir = rst
 build-dir  = doc
-
diff --git a/setup.py b/setup.py
index a1a616b..4e19cfe 100755
--- a/setup.py
+++ b/setup.py
@@ -46,8 +46,13 @@
 basedir = os.path.abspath(os.path.dirname(sys.argv[0]))
 sys.path.insert(0, os.path.join(basedir, 'util'))
 
-# When running from HG repo, enable all warnings
-DEVELOPER_MODE = os.path.exists(os.path.join(basedir, 'MANIFEST.in'))
+ON_TRAVIS = os.environ.get('TRAVIS_OS_NAME') is not None
+
+# when running on developer machine / from a repo checkout:
+# enable all warnings, abort on some warnings.
+# when running on travis-ci, do not use developer mode, so it
+# can compile and test even if there are e.g. deprecation warnings.
+DEVELOPER_MODE = os.path.exists(os.path.join(basedir, 'MANIFEST.in')) and not ON_TRAVIS
 if DEVELOPER_MODE:
     print('found MANIFEST.in, running in developer mode')
     warnings.resetwarnings()
@@ -140,6 +145,13 @@ def main():
           classifiers=['Development Status :: 4 - Beta',
                        'Intended Audience :: Developers',
                        'Programming Language :: Python',
+                       'Programming Language :: Python :: 3',
+                       'Programming Language :: Python :: 3.4',
+                       'Programming Language :: Python :: 3.5',
+                       'Programming Language :: Python :: 3.6',
+                       'Programming Language :: Python :: 3.7',
+                       'Programming Language :: Python :: 3.8',
+                       'Programming Language :: Python :: 3.9',
                        'Topic :: Software Development :: Libraries :: Python Modules',
                        'Topic :: System :: Filesystems',
                        'License :: OSI Approved :: GNU Library or Lesser General Public License (LGPL)',
@@ -231,8 +243,9 @@ def run(self):
             raise SystemExit('Cython needs to be installed for this command')
 
         hit = re.match('^Cython version (.+)$', version)
-        if not hit or LooseVersion(hit.group(1)) < "0.24":
-            raise SystemExit('Need Cython 0.24 or newer, found ' + version)
+        if not hit or LooseVersion(hit.group(1)) < "0.29":
+            # in fact, we need a very recent Cython version (like 0.29.21) to support py39
+            raise SystemExit('Need Cython 0.29 or newer, found ' + version)
 
         cmd = ['cython', '-Wextra', '--force', '-3', '--fast-fail',
                '--directive', 'embedsignature=True', '--include-dir',
diff --git a/test/travis-install.sh b/test/travis-install.sh
index 32c6fec..4d98d12 100755
--- a/test/travis-install.sh
+++ b/test/travis-install.sh
@@ -2,5 +2,6 @@
 
 set -e
 
-pip install pytest cython sphinx
+# as long as we test on python 3.4, we need pytest < 5.0
+pip install 'pytest<5.0' pytest-catchlog cython sphinx
 cython --version