diff --git a/build_library/legacy_disk_layout.json b/build_library/legacy_disk_layout.json
index 5648d59978..78b7bea5fe 100644
--- a/build_library/legacy_disk_layout.json
+++ b/build_library/legacy_disk_layout.json
@@ -172,7 +172,7 @@
         "num": 5,
         "label":"ROOT-B",
         "type":"rootfs",
-        "blocks":"1"
+        "blocks":"4096"
       }
     ],
     "2gb-rootfs": [