diff --git a/configs/workhorse/prometheus.nix b/configs/workhorse/prometheus.nix
index 6626193..611f855 100644
--- a/configs/workhorse/prometheus.nix
+++ b/configs/workhorse/prometheus.nix
@@ -12,6 +12,8 @@
 
   services.prometheus = {
     enable = true;
+    # keep data for 30 days
+    extraFlags = "--storage.tsdb.retention.time=30d"
     scrapeConfigs = [
       {
         job_name = "nginx";