--- a/mobile/android/base/java/org/mozilla/gecko/push/PushService.java
+++ b/mobile/android/base/java/org/mozilla/gecko/push/PushService.java
@@ -208,25 +208,27 @@ public class PushService implements Bund
             Log.e(LOG_TAG, "callback must not be null in " + event);
             return;
         }
 
         try {
             if ("PushServiceAndroidGCM:Configure".equals(event)) {
                 final String endpoint = message.getString("endpoint");
                 if (endpoint == null) {
-                    Log.e(LOG_TAG, "endpoint must not be null in " + event);
+                    callback.sendError("endpoint must not be null in " + event);
                     return;
                 }
                 final boolean debug = message.getBoolean("debug", false);
                 pushManager.configure(geckoProfile.getName(), endpoint, debug, System.currentTimeMillis()); // For side effects.
                 callback.sendSuccess(null);
                 return;
             }
             if ("PushServiceAndroidGCM:DumpRegistration".equals(event)) {
+                // In the future, this might be used to interrogate the Java Push Manager
+                // registration state from JavaScript.
                 callback.sendError("Not yet implemented!");
                 return;
             }
             if ("PushServiceAndroidGCM:DumpSubscriptions".equals(event)) {
                 try {
                     final Map<String, PushSubscription> result = pushManager.allSubscriptionsForProfile(geckoProfile.getName());
 
                     final JSONObject json = new JSONObject();
@@ -245,16 +247,20 @@ public class PushService implements Bund
                     callback.sendSuccess(null);
                 } catch (PushManager.ProfileNeedsConfigurationException | AutopushClientException | PushClient.LocalException | IOException e) {
                     Log.e(LOG_TAG, "Got exception in " + event, e);
                     callback.sendError("Got exception handling message [" + event + "]: " + e.toString());
                 }
                 return;
             }
             if ("PushServiceAndroidGCM:UnregisterUserAgent".equals(event)) {
+                // In the future, this might be used to tell the Java Push Manager to unregister
+                // a User Agent entirely from JavaScript.  Right now, however, everything is
+                // subscription based; there's no concept of unregistering all subscriptions
+                // simultaneously.
                 callback.sendError("Not yet implemented!");
                 return;
             }
             if ("PushServiceAndroidGCM:SubscribeChannel".equals(event)) {
                 final String service = SERVICE_WEBPUSH;
                 final JSONObject serviceData;
                 try {
                     serviceData = new JSONObject();
@@ -283,17 +289,30 @@ public class PushService implements Bund
                     Log.e(LOG_TAG, "Got exception in " + event, e);
                     callback.sendError("Got exception handling message [" + event + "]: " + e.toString());
                     return;
                 }
                 callback.sendSuccess(json);
                 return;
             }
             if ("PushServiceAndroidGCM:UnsubscribeChannel".equals(event)) {
-                callback.sendError("Not yet implemented!");
+                final String channelID = message.getString("channelID");
+                if (channelID == null) {
+                    callback.sendError("channelID must not be null in " + event);
+                    return;
+                }
+
+                // Fire and forget.  See comments in the function itself.
+                final PushSubscription pushSubscription = pushManager.unsubscribeChannel(channelID);
+                if (pushSubscription != null) {
+                    callback.sendSuccess(null);
+                    return;
+                }
+
+                callback.sendError("Could not unsubscribe from channel: " + channelID);
                 return;
             }
         } catch (GcmTokenClient.NeedsGooglePlayServicesException e) {
             // TODO: improve this.  Can we find a point where the user is *definitely* interacting
             // with the WebPush?  Perhaps we can show a dialog when interacting with the Push
             // permissions, and then be more aggressive showing this notification when we have
             // registrations and subscriptions that can't be advanced.
             callback.sendError("To handle event [" + event + "], user interaction is needed to enable Google Play Services.");