diff --git a/py34/bacpypes/service/cov.py b/py34/bacpypes/service/cov.py
index 160223b..4a5e320 100644
--- a/py34/bacpypes/service/cov.py
+++ b/py34/bacpypes/service/cov.py
@@ -680,6 +680,83 @@ class ChangeOfValueServices(Capability):
 
         ### delete the rest of the pending requests for this client
 
+    def do_SubscribeCOVRequest(self, apdu):
+        if _debug: ChangeOfValueServices._debug("do_SubscribeCOVRequest %r", apdu)
+
+        # extract the pieces
+        client_addr = apdu.pduSource
+        proc_id = apdu.subscriberProcessIdentifier
+        obj_id = apdu.monitoredObjectIdentifier
+        confirmed = apdu.issueConfirmedNotifications
+        lifetime = apdu.lifetime
+
+        # request is to cancel the subscription
+        cancel_subscription = (confirmed is None) and (lifetime is None)
+
+        # find the object
+        obj = self.get_object_id(obj_id)
+        if _debug: ChangeOfValueServices._debug("    - object: %r", obj)
+        if not obj:
+            raise ExecutionError(errorClass='object', errorCode='unknownObject')
+
+        # check to see if the object supports COV
+        if not obj._object_supports_cov:
+            raise ExecutionError(errorClass='services', errorCode='covSubscriptionFailed')
+
+        # look for an algorithm already associated with this object
+        cov_detection = self.cov_detections.get(obj, None)
+
+        # if there isn't one, make one and associate it with the object
+        if not cov_detection:
+            # look for an associated class and if it's not there it's not supported
+            criteria_class = criteria_type_map.get(obj_id[0], None)
+            if not criteria_class:
+                raise ExecutionError(errorClass='services', errorCode='covSubscriptionFailed')
+
+            # make one of these and bind it to the object
+            cov_detection = criteria_class(obj)
+
+            # keep track of it for other subscriptions
+            self.cov_detections[obj] = cov_detection
+        if _debug: ChangeOfValueServices._debug("    - cov_detection: %r", cov_detection)
+
+        # can a match be found?
+        cov = cov_detection.cov_subscriptions.find(client_addr, proc_id, obj_id)
+        if _debug: ChangeOfValueServices._debug("    - cov: %r", cov)
+
+        # if a match was found, update the subscription
+        if cov:
+            if cancel_subscription:
+                if _debug: ChangeOfValueServices._debug("    - cancel the subscription")
+                self.cancel_subscription(cov)
+            else:
+                if _debug: ChangeOfValueServices._debug("    - renew the subscription")
+                cov.renew_subscription(lifetime)
+        else:
+            if cancel_subscription:
+                if _debug: ChangeOfValueServices._debug("    - cancel a subscription that doesn't exist")
+            else:
+                if _debug: ChangeOfValueServices._debug("    - create a subscription")
+
+                # make a subscription
+                cov = Subscription(obj, client_addr, proc_id, obj_id, confirmed, lifetime, None)
+                if _debug: ChangeOfValueServices._debug("    - cov: %r", cov)
+
+                # add it to our subscriptions lists
+                self.add_subscription(cov)
+
+        # success
+        response = SimpleAckPDU(context=apdu)
+
+        # return the result
+        self.response(response)
+
+        # if the subscription is not being canceled, it is new or renewed,
+        # so send it a notification when you get a chance.
+        if not cancel_subscription:
+            if _debug: ChangeOfValueServices._debug("    - send a notification")
+            deferred(cov_detection.send_cov_notifications, cov)
+
     def do_SubscribeCOVPropertyRequest(self, apdu):
         if _debug: ChangeOfValueServices._debug("do_SubscribeCOVPropertyRequest %r", apdu)