diff --git a/.rubocop.yml b/.rubocop.yml
index 0b7308a3..c60cd809 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -178,9 +178,6 @@ Style/ClassAndModuleChildren:
 Style/MissingRespondToMissing:
   Enabled: false
 
-Style/OpenStructUse:
-  Enabled: false
-
 Style/OptionalBooleanParameter:
   Enabled: false
 
diff --git a/lib/jira/client.rb b/lib/jira/client.rb
index a4a206ca..17ebbecf 100644
--- a/lib/jira/client.rb
+++ b/lib/jira/client.rb
@@ -2,7 +2,6 @@
 
 require 'json'
 require 'forwardable'
-require 'ostruct'
 
 module JIRA
   # This class is the main access point for all JIRA::Resource instances.
@@ -55,7 +54,7 @@ class Client
     #
     # The authenticated client instance returned by the respective client type
     # (Oauth, Basic)
-    attr_accessor :consumer, :request_client, :http_debug, :cache
+    attr_accessor :consumer, :request_client, :http_debug, :field_map_cache
 
     # The configuration options for this client instance
     attr_reader :options
@@ -164,8 +163,6 @@ def initialize(options = {})
       @http_debug = @options[:http_debug]
 
       @options.freeze
-
-      @cache = OpenStruct.new
     end
 
     def Project # :nodoc:
diff --git a/lib/jira/resource/field.rb b/lib/jira/resource/field.rb
index f9c841ea..b3186ea9 100644
--- a/lib/jira/resource/field.rb
+++ b/lib/jira/resource/field.rb
@@ -21,7 +21,6 @@ def self.safer_name(description, jira_id)
 
       def self.map_fields(client)
         field_map = {}
-        field_map_reverse = {}
         fields = client.Field.all
 
         # two pass approach, so that a custom field with the same name
@@ -30,7 +29,6 @@ def self.map_fields(client)
           next if f.custom
 
           name = safe_name(f.name)
-          field_map_reverse[f.id] = [f.name, name] # capture both the official name, and the mapped name
           field_map[name] = f.id
         end
 
@@ -44,23 +42,21 @@ def self.map_fields(client)
                  else
                    safe_name(f.name)
                  end
-          field_map_reverse[f.id] = [f.name, name] # capture both the official name, and the mapped name
           field_map[name] = f.id
         end
 
-        client.cache.field_map_reverse = field_map_reverse # not sure where this will be used yet, but sure to be useful
-        client.cache.field_map = field_map
+        client.field_map_cache = field_map
       end
 
       def self.field_map(client)
-        client.cache.field_map
+        client.field_map_cache
       end
 
       def self.name_to_id(client, field_name)
         field_name = field_name.to_s
-        return field_name unless client.cache.field_map && client.cache.field_map[field_name]
+        return field_name unless client.field_map_cache && client.field_map_cache[field_name]
 
-        client.cache.field_map[field_name]
+        client.field_map_cache[field_name]
       end
 
       def respond_to?(method_name, _include_all = false)
diff --git a/spec/integration/user_spec.rb b/spec/integration/user_spec.rb
index 5f9a716a..788a342b 100644
--- a/spec/integration/user_spec.rb
+++ b/spec/integration/user_spec.rb
@@ -41,7 +41,7 @@
 
       before do
         allow(client).to receive(:get)
-          .with('/rest/api/2/users/search?username=_&maxResults=1000') { OpenStruct.new(body: '["User1"]') }
+          .with('/rest/api/2/users/search?username=_&maxResults=1000') { double(body: '["User1"]') }
         allow(client).to receive_message_chain(:User, :build).with('users') { [] }
       end
 
diff --git a/spec/jira/resource/board_spec.rb b/spec/jira/resource/board_spec.rb
index df5f3780..1c9096c1 100644
--- a/spec/jira/resource/board_spec.rb
+++ b/spec/jira/resource/board_spec.rb
@@ -107,7 +107,7 @@ class JIRAResourceDelegation < SimpleDelegator # :nodoc:
 
       context 'when there are multiple pages of results' do
         let(:result_1) do
-          OpenStruct.new(body: {
+          double(body: {
             'startAt' => 0,
             'maxResults' => 1,
             'total' => 2,
@@ -115,7 +115,7 @@ class JIRAResourceDelegation < SimpleDelegator # :nodoc:
           }.to_json)
         end
         let(:result_2) do
-          OpenStruct.new(body: {
+          double(body: {
             'startAt' => 1,
             'maxResults' => 1,
             'total' => 2,
@@ -132,7 +132,7 @@ class JIRAResourceDelegation < SimpleDelegator # :nodoc:
 
       context 'when there is only one page of results' do
         let(:result_1) do
-          OpenStruct.new(body: {
+          double(body: {
             'startAt' => 0,
             'maxResults' => 2,
             'total' => 2,
diff --git a/spec/jira/resource/field_spec.rb b/spec/jira/resource/field_spec.rb
index 01a43a43..f3295d99 100644
--- a/spec/jira/resource/field_spec.rb
+++ b/spec/jira/resource/field_spec.rb
@@ -1,13 +1,12 @@
 require 'spec_helper'
 
 describe JIRA::Resource::Field do
-  let(:cache) { OpenStruct.new }
-
   let(:client) do
     client = double(options: { rest_base_path: '/jira/rest/api/2' })
     field = JIRA::Resource::FieldFactory.new(client)
     allow(client).to receive(:Field).and_return(field)
-    allow(client).to receive(:cache).and_return(cache)
+    allow(client).to receive(:field_map_cache).and_return(nil)
+    allow(client).to receive(:field_map_cache=)
     # info about all fields on the client
     allow(client.Field).to receive(:all).and_return([
                                                       described_class.new(client,
diff --git a/spec/jira/resource/issue_spec.rb b/spec/jira/resource/issue_spec.rb
index 2943ab1d..cbb7cd5e 100644
--- a/spec/jira/resource/issue_spec.rb
+++ b/spec/jira/resource/issue_spec.rb
@@ -7,7 +7,7 @@ class JIRAResourceDelegation < SimpleDelegator # :nodoc:
   let(:client) do
     client = double(options: { rest_base_path: '/jira/rest/api/2' })
     allow(client).to receive(:Field).and_return(JIRA::Resource::FieldFactory.new(client))
-    allow(client).to receive(:cache).and_return(OpenStruct.new)
+    allow(client).to receive(:field_map_cache).and_return(nil)
     client
   end
 
diff --git a/spec/jira/resource/status_spec.rb b/spec/jira/resource/status_spec.rb
index de2652fe..25de117e 100644
--- a/spec/jira/resource/status_spec.rb
+++ b/spec/jira/resource/status_spec.rb
@@ -4,7 +4,7 @@
   let(:client) do
     client = double(options: { rest_base_path: '/jira/rest/api/2' })
     allow(client).to receive(:Field).and_return(JIRA::Resource::FieldFactory.new(client))
-    allow(client).to receive(:cache).and_return(OpenStruct.new)
+    allow(client).to receive(:field_map_cache).and_return(nil)
     client
   end