diff --git a/pageserver/src/disk_usage_eviction_task.rs b/pageserver/src/disk_usage_eviction_task.rs
index df563b5082..8a0e03094c 100644
--- a/pageserver/src/disk_usage_eviction_task.rs
+++ b/pageserver/src/disk_usage_eviction_task.rs
@@ -592,6 +592,7 @@ async fn collect_eviction_candidates(
         }
     }
 
+    debug_assert!(MinResidentSizePartition::Above < MinResidentSizePartition::Below);
     candidates
         .sort_unstable_by_key(|(partition, candidate)| (*partition, candidate.last_activity_ts));