diff --git a/rg_tool.py b/rg_tool.py
index 92c62ba70..0edb12336 100755
--- a/rg_tool.py
+++ b/rg_tool.py
@@ -84,7 +84,8 @@ def build_image(apps, device_type, img_format="esp32", fatsize=0):
         image_data += data + b"\xFF" * (part_size - len(data))
 
     if fatsize:
-        table_csv.append("vfs, data, fat, , " + args.fatsize + ","); # Use "vfs" label, same as MicroPython, in case the storage is to be shared with a MicroPython install
+        # Use "vfs" label, same as MicroPython, in case the storage is to be shared with a MicroPython install
+        table_csv.append("vfs, data, fat, %d, %d" % (len(image_data), fatsize))
 
     print("Generating partition table...")
     with open("partitions.csv", "w") as f: