diff --git a/acceptance/tests/resource/service/ticket_5024_systemd_enabling_masked_service.rb b/acceptance/tests/resource/service/ticket_5024_systemd_enabling_masked_service.rb
index 8c989ea0dd7..30ce975d864 100644
--- a/acceptance/tests/resource/service/ticket_5024_systemd_enabling_masked_service.rb
+++ b/acceptance/tests/resource/service/ticket_5024_systemd_enabling_masked_service.rb
@@ -17,6 +17,7 @@
 package_name = {'el'     => 'httpd',
                 'centos' => 'httpd',
                 'fedora' => 'httpd',
+                'amazon' => 'httpd',
                 'sles'   => 'apache2',
                 'debian' => 'cron', # apache2 does not create systemd service symlinks in Debian
                 'ubuntu' => 'cron', # See https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1447807
@@ -43,13 +44,6 @@
     package { '#{package_name[platform]}':
       ensure => present,
     }
-    if ($os['name'] == 'Fedora') and ($os['release']['major'] == '23') {
-      package{'libnghttp2':
-        ensure => latest,
-        install_options => '--best',
-        before => Package['httpd'],
-      }
-    }
   }
   manifest_service_masked = %Q{
     service { '#{package_name[platform]}':
diff --git a/lib/puppet/settings.rb b/lib/puppet/settings.rb
index bde9f7875a4..9876ffc7b80 100644
--- a/lib/puppet/settings.rb
+++ b/lib/puppet/settings.rb
@@ -6,6 +6,7 @@
 require 'forwardable'
 require 'fileutils'
 require 'concurrent'
+require_relative 'concurrent/lock'
 
 # The class for handling configuration files.
 class Puppet::Settings
@@ -147,8 +148,21 @@ def initialize
     @configuration_file = nil
 
     # And keep a per-environment cache
-    @cache = Concurrent::Hash.new { |hash, key| hash[key] = Concurrent::Hash.new }
-    @values = Concurrent::Hash.new { |hash, key| hash[key] = Concurrent::Hash.new }
+    # We can't use Concurrent::Map because we want to preserve insertion order
+    @cache_lock = Puppet::Concurrent::Lock.new
+    @cache = Concurrent::Hash.new do |hash, key|
+      @cache_lock.synchronize do
+        break hash[key] if hash.key?(key)
+        hash[key] = Concurrent::Hash.new
+      end
+    end
+    @values_lock = Puppet::Concurrent::Lock.new
+    @values = Concurrent::Hash.new do |hash, key|
+      @values_lock.synchronize do
+        break hash[key] if hash.key?(key)
+        hash[key] = Concurrent::Hash.new
+      end
+    end
 
     # The list of sections we've used.
     @used = []