diff --git a/pageserver/src/layered_repository/inmemory_layer.rs b/pageserver/src/layered_repository/inmemory_layer.rs
index 577e562115..dc1177e76c 100644
--- a/pageserver/src/layered_repository/inmemory_layer.rs
+++ b/pageserver/src/layered_repository/inmemory_layer.rs
@@ -335,11 +335,13 @@ impl InMemoryLayer {
             self.start_lsn..inner.end_lsn.unwrap(),
         )?;
 
+        let mut buf = Vec::new();
         let mut do_steps = || -> Result<()> {
             for (key, vec_map) in inner.index.iter() {
                 // Write all page versions
                 for (lsn, pos) in vec_map.as_slice() {
-                    let val = Value::des(&utils::read_blob(&inner.file, *pos)?)?;
+                    let len = utils::read_blob_buf(&inner.file, *pos, &mut buf)?;
+                    let val = Value::des(&buf[0..len])?;
                     delta_layer_writer.put_value(*key, *lsn, val)?;
                 }
             }
diff --git a/pageserver/src/layered_repository/utils.rs b/pageserver/src/layered_repository/utils.rs
index de6303ce35..b3aa8c7ef4 100644
--- a/pageserver/src/layered_repository/utils.rs
+++ b/pageserver/src/layered_repository/utils.rs
@@ -4,17 +4,22 @@ use std::os::unix::fs::FileExt;
 
 use bookfile::BoundedReader;
 
-pub fn read_blob<F: FileExt>(file: &F, off: u64) -> Result<Vec<u8>, Error> {
+pub fn read_blob_buf<F: FileExt>(file: &F, off: u64, buf: &mut Vec<u8>) -> Result<usize, Error> {
     // read length
     let mut len_buf = [0u8; 4];
     file.read_exact_at(&mut len_buf, off)?;
 
-    let len = u32::from_ne_bytes(len_buf);
+    let len = u32::from_ne_bytes(len_buf) as usize;
 
-    let mut buf: Vec<u8> = Vec::new();
-    buf.resize(len as usize, 0);
+    buf.resize(len, 0);
     file.read_exact_at(&mut buf.as_mut_slice(), off + 4)?;
 
+    Ok(len)
+}
+
+pub fn read_blob<F: FileExt>(file: &F, off: u64) -> Result<Vec<u8>, Error> {
+    let mut buf: Vec<u8> = Vec::new();
+    let _ = read_blob_buf(file, off, &mut buf);
     Ok(buf)
 }