diff --git a/pageserver/src/tenant/size.rs b/pageserver/src/tenant/size.rs
index cdd5b0cbe7..b2338b620e 100644
--- a/pageserver/src/tenant/size.rs
+++ b/pageserver/src/tenant/size.rs
@@ -60,10 +60,6 @@ pub(crate) enum CalculateSyntheticSizeError {
     #[error(transparent)]
     Fatal(anyhow::Error),
 
-    /// The LSN we are trying to calculate a size at no longer exists at the point we query it
-    #[error("Could not find size at {lsn} in timeline {timeline_id}")]
-    LsnNotFound { timeline_id: TimelineId, lsn: Lsn },
-
     /// Tenant shut down while calculating size
     #[error("Cancelled")]
     Cancelled,
@@ -375,9 +371,8 @@ pub(super) async fn gather_inputs(
 
 /// Augment 'segments' with logical sizes
 ///
-/// this will probably conflict with on-demand downloaded layers, or at least force them all
-/// to be downloaded
-///
+/// This will leave segments' sizes as None if the Timeline associated with the segment is deleted concurrently
+/// (i.e. we cannot read its logical size at a particular LSN).
 async fn fill_logical_sizes(
     timelines: &[Arc<Timeline>],
     segments: &mut [SegmentMeta],
@@ -498,8 +493,6 @@ async fn fill_logical_sizes(
 
         if let Some(Some(size)) = sizes_needed.get(&(timeline_id, lsn)) {
             seg.segment.size = Some(*size);
-        } else {
-            return Err(CalculateSyntheticSizeError::LsnNotFound { timeline_id, lsn });
         }
     }
     Ok(())
diff --git a/test_runner/regress/test_pageserver_metric_collection.py b/test_runner/regress/test_pageserver_metric_collection.py
index b0465f2a96..cea35a6acb 100644
--- a/test_runner/regress/test_pageserver_metric_collection.py
+++ b/test_runner/regress/test_pageserver_metric_collection.py
@@ -75,9 +75,6 @@ def test_metric_collection(
     env.pageserver.allowed_errors.extend(
         [
             ".*metrics endpoint refused the sent metrics*",
-            # we have a fast rate of calculation, these can happen at shutdown
-            ".*synthetic_size_worker:calculate_synthetic_size.*:gather_size_inputs.*: failed to calculate logical size at .*: cancelled.*",
-            ".*synthetic_size_worker: failed to calculate synthetic size for tenant .*: failed to calculate some logical_sizes",
             ".*metrics_collection: failed to upload to S3: Failed to upload data of length .* to storage path.*",
         ]
     )
@@ -238,9 +235,6 @@ def test_metric_collection_cleans_up_tempfile(
     env.pageserver.allowed_errors.extend(
         [
             ".*metrics endpoint refused the sent metrics*",
-            # we have a fast rate of calculation, these can happen at shutdown
-            ".*synthetic_size_worker:calculate_synthetic_size.*:gather_size_inputs.*: failed to calculate logical size at .*: cancelled.*",
-            ".*synthetic_size_worker: failed to calculate synthetic size for tenant .*: failed to calculate some logical_sizes",
         ]
     )