diff --git a/tcga_downloader/manifest.py b/tcga_downloader/manifest.py
index ea02456..de69973 100644
--- a/tcga_downloader/manifest.py
+++ b/tcga_downloader/manifest.py
@@ -54,4 +54,8 @@ def load_manifest(path: Path) -> List[ManifestRecord]:
 
     with path.open("r", newline="") as f:
         reader = csv.DictReader(f, delimiter="\t")
-        return [ManifestRecord(**row) for row in reader]
+        records: List[ManifestRecord] = []
+        for row in reader:
+            row["size"] = int(row["size"])
+            records.append(ManifestRecord(**row))
+        return records