diff --git a/hosts/prometheus-hel/services/prometheus.nix b/hosts/prometheus-hel/services/prometheus.nix
index 35daedb..6bbd135 100644
--- a/hosts/prometheus-hel/services/prometheus.nix
+++ b/hosts/prometheus-hel/services/prometheus.nix
@@ -102,7 +102,11 @@ in {
   services.prometheus = {
     enable = true;
     # spindle attaches trace ids as exemplars to its latency histograms
-    extraFlags = ["--enable-feature=exemplar-storage"];
+    retentionTime = "7d";
+    extraFlags = [
+      "--enable-feature=exemplar-storage"
+      "--storage.tsdb.retention.size=35GB"
+    ];
     globalConfig.scrape_interval = "15s";
     scrapeConfigs = [
       {