diff --git a/assemble_floppy.py b/assemble_floppy.py
index 44e0f53..7ffd355 100644
--- a/assemble_floppy.py
+++ b/assemble_floppy.py
@@ -4,6 +4,7 @@ import os.path
 floppy_bytes = 1440 * 1024
 sector_bytes = 512
 dirent_bytes = 32
+file_bytes = sector_bytes * 128
 
 floppy = bytearray()
 
@@ -52,7 +53,7 @@ assert len(directory) <= sector_bytes
 extend_padded(floppy, sector_bytes, directory)
 
 for file_contents in files:
-	extend_padded(floppy, sector_bytes, file_contents)
+	extend_padded(floppy, file_bytes, file_contents)
 
 assert len(floppy) <= floppy_bytes