diff --git a/manifests/fpm/pool.pp b/manifests/fpm/pool.pp
index 3c1a979e..e69a7131 100644
--- a/manifests/fpm/pool.pp
+++ b/manifests/fpm/pool.pp
@@ -121,50 +121,50 @@
 #   '/etc/php5/fpm/pool.d' or '/etc/php-fpm.d'
 #
 define php::fpm::pool (
-  Enum['present', 'absent'] $ensure        = 'present',
-  String[1] $listen                        = '127.0.0.1:9000',
-  Integer[-1] $listen_backlog              = -1,
-  Optional[String[1]] $listen_allowed_clients = undef,
-  Optional[String[1]] $listen_owner        = undef,
-  Optional[String[1]] $listen_group        = undef,
-  Optional[Stdlib::Filemode] $listen_mode  = undef,
-  String[1] $user                          = $php::fpm::config::user,
-  String[1] $group                         = $php::fpm::config::group,
-  Optional[String[1]] $apparmor_hat        = undef,
-  String[1] $pm                            = 'dynamic',
-  Integer[1] $pm_max_children              = 50,
-  Integer[0] $pm_start_servers             = 5,
-  Integer[0] $pm_min_spare_servers         = 5,
-  Integer[0] $pm_max_spare_servers         = 35,
-  Integer[0] $pm_max_requests              = 0,
-  Php::Duration $pm_process_idle_timeout   = '10s',
-  Optional[Stdlib::Absolutepath] $pm_status_path = undef,
-  Optional[Stdlib::Absolutepath] $ping_path = undef,
-  String[1] $ping_response                 = 'pong',
-  Optional[Stdlib::Absolutepath] $access_log = undef,
-  String[1] $access_log_format             = '"%R - %u %t \"%m %r\" %s"',
-  Php::Duration $request_terminate_timeout = 0,
-  Php::Duration $request_slowlog_timeout   = 0,
-  Array[String[1]] $security_limit_extensions = [],
-  Stdlib::Absolutepath $slowlog            = "/var/log/php-fpm/${name}-slow.log",
-  String[1] $template                      = 'php/fpm/pool.conf.erb',
-  Optional[Integer] $rlimit_files          = undef,
-  Optional[Integer] $rlimit_core           = undef,
-  Optional[Stdlib::Absolutepath] $chroot   = undef,
-  Optional[Stdlib::Absolutepath] $chdir    = undef,
-  Enum['yes', 'no'] $catch_workers_output  = 'no',
-  Optional[String[1]] $include             = undef,
-  Array[String[1]] $env                    = [],
-  Hash $env_value                          = {},
-  Boolean $clear_env                       = true,
-  Hash $options                            = {},
-  Hash $php_value                          = {},
-  Hash $php_flag                           = {},
-  Hash $php_admin_value                    = {},
-  Hash $php_admin_flag                     = {},
-  Array[String[1]] $php_directives         = [],
-  String[1] $root_group                    = $php::params::root_group,
-  Optional[Stdlib::Absolutepath] $base_dir = undef,
+  Enum['present', 'absent'] $ensure                                 = 'present',
+  String[1] $listen                                                 = '127.0.0.1:9000',
+  Integer[-1] $listen_backlog                                       = -1,
+  Optional[String[1]] $listen_allowed_clients                       = undef,
+  Optional[String[1]] $listen_owner                                 = undef,
+  Optional[String[1]] $listen_group                                 = undef,
+  Optional[Stdlib::Filemode] $listen_mode                           = undef,
+  String[1] $user                                                   = $php::fpm::config::user,
+  String[1] $group                                                  = $php::fpm::config::group,
+  Optional[String[1]] $apparmor_hat                                 = undef,
+  String[1] $pm                                                     = 'dynamic',
+  Variant[Integer[1], Php::EnvString] $pm_max_children              = 50,
+  Variant[Integer[0], Php::EnvString] $pm_start_servers             = 5,
+  Variant[Integer[0], Php::EnvString] $pm_min_spare_servers         = 5,
+  Variant[Integer[0], Php::EnvString] $pm_max_spare_servers         = 35,
+  Variant[Integer[0], Php::EnvString] $pm_max_requests              = 0,
+  Variant[Php::Duration, Php::EnvString] $pm_process_idle_timeout   = '10s',
+  Optional[Stdlib::Absolutepath] $pm_status_path                    = undef,
+  Optional[Stdlib::Absolutepath] $ping_path                         = undef,
+  String[1] $ping_response                                          = 'pong',
+  Optional[Stdlib::Absolutepath] $access_log                        = undef,
+  String[1] $access_log_format                                      = '"%R - %u %t \"%m %r\" %s"',
+  Variant[Php::Duration, Php::EnvString] $request_terminate_timeout = 0,
+  Variant[Php::Duration, Php::EnvString] $request_slowlog_timeout   = 0,
+  Array[String[1]] $security_limit_extensions                       = [],
+  Stdlib::Absolutepath $slowlog                                     = "/var/log/php-fpm/${name}-slow.log",
+  String[1] $template                                               = 'php/fpm/pool.conf.erb',
+  Optional[Integer] $rlimit_files                                   = undef,
+  Optional[Integer] $rlimit_core                                    = undef,
+  Optional[Stdlib::Absolutepath] $chroot                            = undef,
+  Optional[Stdlib::Absolutepath] $chdir                             = undef,
+  Enum['yes', 'no'] $catch_workers_output                           = 'no',
+  Optional[String[1]] $include                                      = undef,
+  Array[String[1]] $env                                             = [],
+  Hash $env_value                                                   = {},
+  Boolean $clear_env                                                = true,
+  Hash $options                                                     = {},
+  Hash $php_value                                                   = {},
+  Hash $php_flag                                                    = {},
+  Hash $php_admin_value                                             = {},
+  Hash $php_admin_flag                                              = {},
+  Array[String[1]] $php_directives                                  = [],
+  String[1] $root_group                                             = $php::params::root_group,
+  Optional[Stdlib::Absolutepath] $base_dir                          = undef,
 ) {
   # The base class must be included first because it is used by parameter defaults
   if ! defined(Class['php']) {
diff --git a/spec/defines/fpm_pool_spec.rb b/spec/defines/fpm_pool_spec.rb
index d6bdd1f0..f1ac17c8 100644
--- a/spec/defines/fpm_pool_spec.rb
+++ b/spec/defines/fpm_pool_spec.rb
@@ -8,6 +8,24 @@
       end
       let(:pre_condition) { 'include php' }
 
+      context 'with environment based config' do
+        let(:title) { 'env-config' }
+        let(:params) { {
+          pm_max_children: '${PM_MAX_CHILDREN}',
+          pm_start_servers: '${PM_START_SERVERS}',
+          pm_min_spare_servers: '${PM_MIN_SPARE_SERVERS}',
+          pm_max_spare_servers: '${PM_MAX_SPARE_SERVERS}',
+          pm_max_requests: '${PM_MAX_REQUESTS}',
+          pm_process_idle_timeout: '${PM_PROCESS_IDLE_TIMEOUT}',
+          request_terminate_timeout: '${REQUEST_TERMINATE_TIMEOUT}',
+          request_slowlog_timeout: '${REQUEST_SLOWLOG_TIMEOUT}',
+        } }
+
+        it {
+          is_expected.to compile
+        }
+      end
+
       case facts[:os]['name']
       when 'Debian'
         context 'plain config' do