diff --git a/pageserver/src/tenant/layer_map/historic_layer_coverage.rs b/pageserver/src/tenant/layer_map/historic_layer_coverage.rs
index b63c361314..8487609a5f 100644
--- a/pageserver/src/tenant/layer_map/historic_layer_coverage.rs
+++ b/pageserver/src/tenant/layer_map/historic_layer_coverage.rs
@@ -490,10 +490,12 @@ impl<Value: Clone> BufferedHistoricLayerCoverage<Value> {
         self.buffer.retain(|layer_key, layer| {
             match layer {
                 Some(l) => {
-                    self.layers.insert(layer_key.clone(), l.clone());
+                    // There should not be duplicate layers
+                    assert!(self.layers.insert(layer_key.clone(), l.clone()).is_none());
                 }
                 None => {
-                    self.layers.remove(layer_key);
+                    // layer is present in the tree
+                    assert!(self.layers.remove(layer_key).is_some());
                 }
             };
             false
diff --git a/pageserver/src/tenant/storage_layer/image_layer.rs b/pageserver/src/tenant/storage_layer/image_layer.rs
index dc98be8c0b..d298b3e852 100644
--- a/pageserver/src/tenant/storage_layer/image_layer.rs
+++ b/pageserver/src/tenant/storage_layer/image_layer.rs
@@ -623,9 +623,6 @@ impl ImageLayerWriterInner {
                 lsn: self.lsn,
             },
         );
-        if final_path.exists() {
-            warn!("Overwrite existed image layer {}", final_path.display());
-        }
         std::fs::rename(self.path, final_path)?;
 
         trace!("created image layer {}", layer.path().display());
diff --git a/pageserver/src/tenant/timeline.rs b/pageserver/src/tenant/timeline.rs
index 28946efd58..1bfd17aae2 100644
--- a/pageserver/src/tenant/timeline.rs
+++ b/pageserver/src/tenant/timeline.rs
@@ -2921,12 +2921,12 @@ impl Timeline {
                 let img_range =
                     partition.ranges.first().unwrap().start..partition.ranges.last().unwrap().end;
                 if wanted.overlaps(&img_range) {
-					//
-					// gc_timeline only pays attention to image layers that are older than the GC cutoff,
-					// but create_image_layers creates image layers at last-record-lsn.
-					// So it's possible that gc_timeline wants a new image layer to be created for a key range,
-					// but the range is already covered by image layers at more recent LSNs. Before we
-					// create a new image layer, check if the range is already covered at more recent LSNs.
+                    //
+                    // gc_timeline only pays attention to image layers that are older than the GC cutoff,
+                    // but create_image_layers creates image layers at last-record-lsn.
+                    // So it's possible that gc_timeline wants a new image layer to be created for a key range,
+                    // but the range is already covered by image layers at more recent LSNs. Before we
+                    // create a new image layer, check if the range is already covered at more recent LSNs.
                     if !layers
                         .image_layer_exists(&img_range, &(Lsn::min(lsn, *cutoff_lsn)..lsn + 1))?
                     {