diff --git a/lib/rackstash/filter/anonymize_ip_mask.rb b/lib/rackstash/filter/anonymize_ip_mask.rb
index c5bb4a8..3b79fb8 100644
--- a/lib/rackstash/filter/anonymize_ip_mask.rb
+++ b/lib/rackstash/filter/anonymize_ip_mask.rb
@@ -8,6 +8,7 @@
 require 'ipaddr'
 
 require 'rackstash/filter'
+require 'rackstash/helpers/utf8'
 
 module Rackstash
   module Filter
@@ -41,6 +42,8 @@ module Rackstash
     #     filter :anonymize_ip_mask, {'source_ip' => 'source_ip'}
     #   end
     class AnonymizeIPMask
+      include Rackstash::Helpers::UTF8
+
       # @param field_spec [Hash<#to_s => #to_s>] a `Hash` specifying which
       #   fields should be anonymized and where the result should be stored. The
       #   key described the name of the existing source field and the value the
@@ -54,7 +57,7 @@ module Rackstash
       def initialize(field_spec, ipv4_mask: 8, ipv6_mask: 80)
         @fields = {}
         Hash(field_spec).each_pair do |key, value|
-          @fields[key.to_s] = value.to_s
+          @fields[utf8_encode(key)] = utf8_encode(value)
         end
 
         @ipv4_mask = Integer(ipv4_mask)
diff --git a/lib/rackstash/filter/rename.rb b/lib/rackstash/filter/rename.rb
index 2156065..8c7d66d 100644
--- a/lib/rackstash/filter/rename.rb
+++ b/lib/rackstash/filter/rename.rb
@@ -1,11 +1,12 @@
 # frozen_string_literal: true
 #
-# Copyright 2017 Holger Just
+# Copyright 2017 - 2018 Holger Just
 #
 # This software may be modified and distributed under the terms
 # of the MIT license. See the LICENSE.txt file for details.
 
 require 'rackstash/filter'
+require 'rackstash/helpers/utf8'
 
 module Rackstash
   module Filter
@@ -17,13 +18,15 @@ module Rackstash
     #     filter :rename, "HOST_OR_IP" => "client_ip"
     #   end
     class Rename
+      include Rackstash::Helpers::UTF8
+
       # @param spec [Hash<#to_s => #to_s>] a `Hash` specifying how fields should
       #   be renamed, with the existing field name as a hash key and the new
       #   field name as the respective value.
       def initialize(spec)
         @rename = {}
         Hash(spec).each_pair do |key, value|
-          @rename[key.to_s] = value.to_s
+          @rename[utf8_encode(key)] = utf8_encode(value)
         end
       end
 
diff --git a/lib/rackstash/filter/replace.rb b/lib/rackstash/filter/replace.rb
index 8b5d31b..6447439 100644
--- a/lib/rackstash/filter/replace.rb
+++ b/lib/rackstash/filter/replace.rb
@@ -1,11 +1,12 @@
 # frozen_string_literal: true
 #
-# Copyright 2017 Holger Just
+# Copyright 2017 - 2018 Holger Just
 #
 # This software may be modified and distributed under the terms
 # of the MIT license. See the LICENSE.txt file for details.
 
 require 'rackstash/filter'
+require 'rackstash/helpers/utf8'
 
 module Rackstash
   module Filter
@@ -30,6 +31,8 @@ module Rackstash
     # here, namely `String`, `Integer`, `Float`, `Hash`, `Array`, `nil`, `true`,
     # or `false`.
     class Replace
+      include Rackstash::Helpers::UTF8
+
       # @param spec [Hash<#to_s => #call,Object>] a `Hash` specifying new field
       #   values for the named keys. Values can be given in the form of a fixed
       #   value or a callable object (e.g. a `Proc`) which accepts the event as
@@ -37,7 +40,7 @@ module Rackstash
       def initialize(spec)
         @replace = {}
         Hash(spec).each_pair do |key, value|
-          @replace[key.to_s] = value
+          @replace[utf8_encode(key)] = value
         end
       end