diff --git a/tools/uncompressedsize.py b/tools/uncompressedsize.py
index 1b6c0e468..608446bae 100644
--- a/tools/uncompressedsize.py
+++ b/tools/uncompressedsize.py
@@ -11,7 +11,7 @@ from util.gzipstream import ZLIB_GZIP_WINDOW
 logger = logging.getLogger(__name__)
 
 
-CHUNK_SIZE = 512 * 1024 * 1024
+CHUNK_SIZE = 5 * 1024 * 1024
 
 
 def backfill_sizes_from_data():