diff --git a/libs/pageserver_api/src/models.rs b/libs/pageserver_api/src/models.rs
index f67aa248eb..fd8931bcda 100644
--- a/libs/pageserver_api/src/models.rs
+++ b/libs/pageserver_api/src/models.rs
@@ -1623,6 +1623,7 @@ pub struct TimelineInfo {
     /// Whether the timeline is invisible in synthetic size calculations.
     pub is_invisible: Option<bool>,
 
+    #[serde(default)]
     pub standby_horizon: serde_json::Value,
 }