diff --git a/src/pylorax/constants.py b/src/pylorax/constants.py
index 677635fc..36b3101e 100644
--- a/src/pylorax/constants.py
+++ b/src/pylorax/constants.py
@@ -73,3 +73,5 @@ class LoraxRequiredCommands(dict):
 K_NORMAL = 0
 K_PAE = 1
 K_XEN = 1
+
+FS_OVERHEAD = 512