diff --git a/libs/pageserver_api/src/models.rs b/libs/pageserver_api/src/models.rs
index 0a7c9717ca..f2dd3a0ebf 100644
--- a/libs/pageserver_api/src/models.rs
+++ b/libs/pageserver_api/src/models.rs
@@ -1418,11 +1418,6 @@ pub struct TimelineInfo {
     pub last_record_lsn: Lsn,
     pub prev_record_lsn: Option<Lsn>,
 
-    /// Legacy field, retained for one version to enable old storage controller to
-    /// decode (it was a mandatory field).
-    #[serde(default, rename = "latest_gc_cutoff_lsn")]
-    pub _unused: Lsn,
-
     /// The LSN up to which GC has advanced: older data may still exist but it is not available for clients.
     /// This LSN is not suitable for deciding where to create branches etc: use [`TimelineInfo::min_readable_lsn`] instead,
     /// as it is easier to reason about.
diff --git a/pageserver/src/http/routes.rs b/pageserver/src/http/routes.rs
index 3f36ff9904..3a3b4202dd 100644
--- a/pageserver/src/http/routes.rs
+++ b/pageserver/src/http/routes.rs
@@ -445,6 +445,9 @@ async fn build_timeline_info_common(
 
     let (pitr_history_size, within_ancestor_pitr) = timeline.get_pitr_history_stats();
 
+    // Externally, expose the lowest LSN that can be used to create a branch.
+    // Internally we distinguish between the planned GC cutoff (PITR point) and the "applied" GC cutoff (where we
+    // actually trimmed data to), which can pass each other when PITR is changed.
     let min_readable_lsn = std::cmp::max(
         timeline.get_gc_cutoff_lsn(),
         *timeline.get_applied_gc_cutoff_lsn(),
@@ -461,7 +464,6 @@ async fn build_timeline_info_common(
         initdb_lsn,
         last_record_lsn,
         prev_record_lsn: Some(timeline.get_prev_record_lsn()),
-        _unused: Default::default(), // Unused, for legacy decode only
         min_readable_lsn,
         applied_gc_cutoff_lsn: *timeline.get_applied_gc_cutoff_lsn(),
         current_logical_size: current_logical_size.size_dont_care_about_accuracy(),