diff --git a/config/config.c b/config/config.c
index 4861d9ead..9b38faf49 100644
--- a/config/config.c
+++ b/config/config.c
@@ -308,12 +308,15 @@ configMessage(DBusConnection *connection, DBusMessage *message, void *closure)
 
         if (ret != BadDrawable && ret != BadAlloc) {
             if (!strlen(dbus_message_get_signature(reply)))
+            {
+                ret = -ret; /* return errors as negative numbers */
                 if (!dbus_message_iter_append_basic(&r_iter, DBUS_TYPE_INT32, &ret)) {
                     ErrorF("[config] couldn't append to iterator\n");
                     dbus_message_unref(reply);
                     dbus_error_free(&error);
                     return DBUS_HANDLER_RESULT_HANDLED;
                 }
+            }
 
             if (!dbus_connection_send(bus, reply, NULL))
                 ErrorF("[config] failed to send reply\n");
diff --git a/config/dbus-api b/config/dbus-api
index cada792f5..654c22bec 100644
--- a/config/dbus-api
+++ b/config/dbus-api
@@ -15,25 +15,23 @@ org.x.config.input:
         Option names beginning with _ are not allowed; they are reserved
         for internal use.
 
-        Returns one int32, which is an X Status, as defined in X.h.  If
-        everything is successful, Success will be returned.  BadMatch will
-        be returned if the options given do not match any device.  BadValue
-        is returned for a malformed message.
+        Returns one signed int32, which is the device id of the new device.
+        If the return value is a negative number, it represents the X
+        Status, as defined in X.h. BadMatch will be returned if the options
+        given do not match any device.  BadValue is returned for a malformed
+        message.  (Example: 8 is new device id 8. -8 is BadMatch.)
 
         Notably, BadAlloc is never returned: the server internally signals
         to D-BUS that the attempt failed for lack of memory.
 
-        The return does not notify the client of which devices were created
-        or modified as a result of this request: clients are encouraged to
-        listen for the XInput DevicePresenceNotify event to monitor changes
-        in the device list.
-
     org.x.config.input.remove:
         Takes one int32 argument, which is the device ID to remove, i.e.:
          i
         is the signature.
-        Same return values as org.x.config.input.add.
+
+        Returns one signed int32 which represents an X status as defined in
+        X.h. See org.x.config.input.add. Error codes are negative numbers.
 
     org.x.config.input.listDevices:
-        Lists the currently active devices.
+        Lists the currently active devices. No argument. 
         Return value is sequence of <id> <name> <id> <name> ...