diff -up nfs-utils-1.3.0/tools/mountstats/mountstats.py.orig nfs-utils-1.3.0/tools/mountstats/mountstats.py

--- nfs-utils-1.3.0/tools/mountstats/mountstats.py.orig	2017-04-08 15:23:53.524215286 -0400

+++ nfs-utils-1.3.0/tools/mountstats/mountstats.py	2017-04-08 15:30:45.862043179 -0400

@@ -565,7 +565,10 @@ class DeviceData:

         for the nfsstat command.

         """

         for op in new_stats.__rpc_data['ops']:

-            self.__rpc_data[op] = list(map(add, self.__rpc_data[op], new_stats.__rpc_data[op]))

+            try:

+                self.__rpc_data[op] = list(map(add, self.__rpc_data[op], new_stats.__rpc_data[op]))

+            except KeyError:

+                continue

     def __print_rpc_op_stats(self, op, sample_time):

         """Print generic stats for one RPC op