diff --git a/pageserver/src/tenant.rs b/pageserver/src/tenant.rs
index 969210622c..ace20e44e2 100644
--- a/pageserver/src/tenant.rs
+++ b/pageserver/src/tenant.rs
@@ -3106,8 +3106,9 @@ impl Tenant {
                     3,
                     u32::MAX,
                     "persist_initdb_tar_zst",
-                    // TODO: use a cancellation token (https://github.com/neondatabase/neon/issues/5066)
-                    backoff::Cancel::new(CancellationToken::new(), || unreachable!()),
+                    backoff::Cancel::new(self.cancel.clone(), || {
+                        anyhow::anyhow!("initdb upload cancelled")
+                    }),
                 )
                 .await?;
 
diff --git a/pageserver/src/tenant/remote_timeline_client/upload.rs b/pageserver/src/tenant/remote_timeline_client/upload.rs
index d0744e7c83..9f5b3c242b 100644
--- a/pageserver/src/tenant/remote_timeline_client/upload.rs
+++ b/pageserver/src/tenant/remote_timeline_client/upload.rs
@@ -4,8 +4,9 @@ use anyhow::{bail, Context};
 use camino::Utf8Path;
 use fail::fail_point;
 use pageserver_api::shard::TenantShardId;
-use std::io::ErrorKind;
+use std::io::{ErrorKind, SeekFrom};
 use tokio::fs::{self, File};
+use tokio::io::AsyncSeekExt;
 
 use super::Generation;
 use crate::{
@@ -119,11 +120,14 @@ pub(crate) async fn upload_initdb_dir(
     storage: &GenericRemoteStorage,
     tenant_id: &TenantId,
     timeline_id: &TimelineId,
-    initdb_tar_zst: File,
+    mut initdb_tar_zst: File,
     size: u64,
 ) -> anyhow::Result<()> {
     tracing::trace!("uploading initdb dir");
 
+    // We might have read somewhat into the file already in the prior retry attempt
+    initdb_tar_zst.seek(SeekFrom::Start(0)).await?;
+
     let file = tokio_util::io::ReaderStream::with_capacity(initdb_tar_zst, super::BUFFER_SIZE);
 
     let remote_path = remote_initdb_archive_path(tenant_id, timeline_id);