diff --git a/.gitignore b/.gitignore
index 6fe00cd..0b0fdad 100644
--- a/.gitignore
+++ b/.gitignore
@@ -15,6 +15,7 @@ nilmdb/server/rbtree.c
 # Setup junk
 dist/
 nilmdb.egg-info/
+venv/
 
 # Misc
 timeit*out
diff --git a/MANIFEST.in b/MANIFEST.in
index 049d13b..618fa2a 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -6,9 +6,13 @@ include versioneer.py
 include Makefile
 include .coveragerc
 include .pylintrc
+include requirements.txt
 
-# Cython files -- include source.
+# Cython files -- include .pyx source, but not the generated .c files
+# (Downstream systems must have cython installed in order to build)
 recursive-include nilmdb/server *.pyx *.pyxdep *.pxd
+exclude nilmdb/server/interval.c
+exclude nilmdb/server/rbtree.c
 
 # Version
 include nilmdb/_version.py
diff --git a/Makefile b/Makefile
index 5d6d303..17af3d0 100644
--- a/Makefile
+++ b/Makefile
@@ -37,7 +37,7 @@ clean::
 	find . -name '*.pyc' -o -name '__pycache__' -print0 | xargs -0 rm -rf
 	rm -f .coverage
 	rm -rf tests/*testdb*
-	rm -rf nilmdb.egg-info/ build/ nilmdb/server/*.so MANIFEST.in
+	rm -rf nilmdb.egg-info/ build/ nilmdb/server/*.so
 	make -C docs clean
 
 gitclean::
diff --git a/README.txt b/README.txt
index a27f220..932fa0f 100644
--- a/README.txt
+++ b/README.txt
@@ -4,9 +4,14 @@ by Jim Paris <jim@jtan.com>
 Prerequisites:
 
   # Runtime and build environments
-  sudo apt install python3.7 python3.7-dev python3-pip
+  sudo apt install python3.7 python3.7-dev python3.7-venv python3-pip
 
-  # Install NilmDB dependencies
+  # Optional: create a new Python virtual environment to isolate
+  # dependencies.  To leave the virtual environment, run "deactivate"
+  python -m venv venv
+  source venv/bin/activate
+
+  # Install all Python dependencies from PyPI.
   pip3 install -r requirements.txt
 
 Test:
diff --git a/requirements.txt b/requirements.txt
index 927ed61..041b4e9 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,4 @@
+cython>=0.29.13
 CherryPy>=18.1.2
 coverage>=4.5.4
 decorator>=4.4.0
diff --git a/setup.py b/setup.py
index 21c7611..36091b4 100755
--- a/setup.py
+++ b/setup.py
@@ -9,15 +9,8 @@
 import traceback
 import sys
 import os
-
-try:
-    from setuptools import setup, find_packages
-    from distutils.extension import Extension
-    import distutils.version
-except ImportError:
-    traceback.print_exc()
-    print("Please install the prerequisites listed in README.txt")
-    sys.exit(1)
+from setuptools import setup
+from distutils.extension import Extension
 
 # Versioneer manages version numbers from git tags.
 # https://github.com/warner/python-versioneer
@@ -28,32 +21,22 @@ import versioneer
 try: import multiprocessing
 except Exception: pass
 
-# Use Cython if it's new enough, otherwise use preexisting C files.
-cython_modules = [ 'nilmdb.server.interval',
-                   'nilmdb.server.rbtree' ]
-try:
-    import Cython
-    from Cython.Build import cythonize
-    if (distutils.version.LooseVersion(Cython.__version__) <
-        distutils.version.LooseVersion("0.16")):
-        print("Cython version", Cython.__version__, "is too old; not using it.")
-        raise ImportError()
-    use_cython = True
-except ImportError:
-    use_cython = False
-
+# External modules that need to be built
 ext_modules = [ Extension('nilmdb.server.rocket', ['nilmdb/server/rocket.c' ]) ]
+
+# Use Cython.
+cython_modules = [ 'nilmdb.server.interval', 'nilmdb.server.rbtree' ]
+import Cython
+from Cython.Build import cythonize
 for modulename in cython_modules:
     filename = modulename.replace('.','/')
-    if use_cython:
-        ext_modules.extend(cythonize(filename + ".pyx"))
-    else:
-        cfile = filename + ".c"
-        if not os.path.exists(cfile):
-            raise Exception("Missing source file " + cfile + ".  "
-                            "Try installing cython >= 0.16.")
-        ext_modules.append(Extension(modulename, [ cfile ]))
+    ext_modules.extend(cythonize(filename + ".pyx"))
 
+# Get list of requirements to use in `install_requires` below.  Note
+# that we don't make a distinction between things that are actually
+# required for end-users vs developers (or use `test_requires` or
+# anything else) -- just install everything for simplicity.
+install_requires = open('requirements.txt').readlines()
 
 # Run setup
 setup(name='nilmdb',
@@ -65,21 +48,8 @@ setup(name='nilmdb',
       long_description = "NILM Database",
       license = "Proprietary",
       author_email = 'jim@jtan.com',
-      tests_require = [ 'nose',
-                        'coverage',
-                        'numpy',
-                        ],
-      setup_requires = [ 'setuptools',
-                         ],
-      install_requires = [ 'decorator',
-                           'cherrypy >= 3.2',
-                           'simplejson',
-                           'python-dateutil',
-                           'pytz',
-                           'psutil >= 0.3.0',
-                           'requests >= 1.1.0',
-                           'progressbar >= 2.2',
-                           ],
+      setup_requires = [ 'setuptools' ],
+      install_requires = install_requires,
       packages = [ 'nilmdb',
                    'nilmdb.utils',
                    'nilmdb.server',