diff --git a/src/s3ql/database.py b/src/s3ql/database.py
index 1c6df119..f3a47781 100644
--- a/src/s3ql/database.py
+++ b/src/s3ql/database.py
@@ -677,7 +677,7 @@ def upload_metadata(
             )
             obj = METADATA_OBJ_NAME % (blockno, params.seq_no)
             fh.seek(blockno * blocksize)
-            backend.write_fh(obj, fh, len_=blocksize)
+            backend.write_fh(obj, fh, len_=min(blocksize, db_size - blockno * blocksize))
 
         if not update_params:
             return