diff --git a/CHANGES.rst b/CHANGES.rst
index 4be6604dd..f1529e79b 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,11 @@
+Changes in synapse v0.23.1 (2017-10-02)
+=======================================
+
+Changes:
+
+* Make 'affinity' package optional, as it is not supported on some platforms
+
+
 Changes in synapse v0.23.0 (2017-10-02)
 =======================================
 
diff --git a/synapse/__init__.py b/synapse/__init__.py
index 97d6c4094..bee4aba62 100644
--- a/synapse/__init__.py
+++ b/synapse/__init__.py
@@ -16,4 +16,4 @@
 """ This is a reference implementation of a Matrix home server.
 """
 
-__version__ = "0.23.0"
+__version__ = "0.23.1"
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index cd0e81591..cf4730730 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -12,10 +12,16 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+
 import gc
 import logging
+import sys
+
+try:
+    import affinity
+except:
+    affinity = None
 
-import affinity
 from daemonize import Daemonize
 from synapse.util import PreserveLoggingContext
 from synapse.util.rlimit import change_resource_limit
@@ -78,6 +84,13 @@ def start_reactor(
         with PreserveLoggingContext():
             logger.info("Running")
             if cpu_affinity is not None:
+                if not affinity:
+                    quit_with_error(
+                        "Missing package 'affinity' required for cpu_affinity\n"
+                        "option\n\n"
+                        "Install by running:\n\n"
+                        "   pip install affinity\n\n"
+                    )
                 logger.info("Setting CPU affinity to %s" % cpu_affinity)
                 affinity.set_process_affinity_mask(0, cpu_affinity)
             change_resource_limit(soft_file_limit)
@@ -97,3 +110,13 @@ def start_reactor(
         daemon.start()
     else:
         run()
+
+
+def quit_with_error(error_string):
+    message_lines = error_string.split("\n")
+    line_length = max([len(l) for l in message_lines if len(l) < 80]) + 2
+    sys.stderr.write("*" * line_length + '\n')
+    for line in message_lines:
+        sys.stderr.write(" %s\n" % (line.rstrip(),))
+    sys.stderr.write("*" * line_length + '\n')
+    sys.exit(1)
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 84ad8f04a..3adf72e14 100755
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -25,6 +25,7 @@ from synapse.api.urls import CONTENT_REPO_PREFIX, FEDERATION_PREFIX, \
     LEGACY_MEDIA_PREFIX, MEDIA_PREFIX, SERVER_KEY_PREFIX, SERVER_KEY_V2_PREFIX, \
     STATIC_PREFIX, WEB_CLIENT_PREFIX
 from synapse.app import _base
+from synapse.app._base import quit_with_error
 from synapse.config._base import ConfigError
 from synapse.config.homeserver import HomeServerConfig
 from synapse.crypto import context_factory
@@ -249,16 +250,6 @@ class SynapseHomeServer(HomeServer):
         return db_conn
 
 
-def quit_with_error(error_string):
-    message_lines = error_string.split("\n")
-    line_length = max([len(l) for l in message_lines if len(l) < 80]) + 2
-    sys.stderr.write("*" * line_length + '\n')
-    for line in message_lines:
-        sys.stderr.write(" %s\n" % (line.rstrip(),))
-    sys.stderr.write("*" * line_length + '\n')
-    sys.exit(1)
-
-
 def setup(config_options):
     """
     Args:
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index 630e92c90..7052333c1 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -40,7 +40,6 @@ REQUIREMENTS = {
     "pymacaroons-pynacl": ["pymacaroons"],
     "msgpack-python>=0.3.0": ["msgpack"],
     "phonenumbers>=8.2.0": ["phonenumbers"],
-    "affinity": ["affinity"],
 }
 CONDITIONAL_REQUIREMENTS = {
     "web_client": {
@@ -59,6 +58,9 @@ CONDITIONAL_REQUIREMENTS = {
     "psutil": {
         "psutil>=2.0.0": ["psutil>=2.0.0"],
     },
+    "affinity": {
+        "affinity": ["affinity"],
+    },
 }