diff --git a/README.md b/README.md
index e6c997e..1da2ce9 100644
--- a/README.md
+++ b/README.md
@@ -31,6 +31,7 @@ CONFIGURATION
 Configurable options:
 - --storage.tsdb.retention.time via `$ps_retention_time`
 - --storage.tsdb.retention.size via `$ps_retention_size`
+- --storage.tsdb.wal-segment-size via `ps_wal_seg_size`
 - authentication user via `$ps_auth_user`
 - authentication password via `$ps_auth_pass`
 - web authentication password via `$ps_web_pass` ( different format required)
diff --git a/manifests/params.pp b/manifests/params.pp
index e655d6e..bfcd81e 100644
--- a/manifests/params.pp
+++ b/manifests/params.pp
@@ -16,6 +16,7 @@
 # @param [String] ps_web_pass the password for web authentication
 # @param [String] ps_retention_time tsdb retention time
 # @param [String] ps_retention_size tsdb retention size
+# @param [String] ps_wal_seg_size WAL segment size
 ##############################################################################
 class prometheus_cd::params (
 
@@ -42,6 +43,7 @@ class prometheus_cd::params (
   # storage
   String $ps_retention_time     = '15d',
   String $ps_retention_size     = '20GB',
+  String $ps_wal_seg_size       = '50MB',
 
 ) {
   # defaults
diff --git a/templates/override.conf.erb b/templates/override.conf.erb
index be35f1a..0766512 100644
--- a/templates/override.conf.erb
+++ b/templates/override.conf.erb
@@ -9,6 +9,7 @@ ExecStart=/usr/bin/prometheus \
   --storage.tsdb.path=/var/lib/prometheus \
   --storage.tsdb.retention.time=<%= @ps_retention_time %> \
   --storage.tsdb.retention.size=<%= @ps_retention_size %> \
+  --storage.tsdb.wal-segment-size=<%= @psps_wal_seg_size %> \
   --web.enable-remote-write-receiver \
   --web.enable-lifecycle \
   --storage.tsdb.wal-compression
\ No newline at end of file