diff --git a/Readme.md b/Readme.md
index 9da71f3..cbefe26 100644
--- a/Readme.md
+++ b/Readme.md
@@ -114,7 +114,7 @@ Therefore, any changes to `cmdline.txt` must be made before the `boot.img` file 
 
 
 #### Create the boot image
-The `-p` product argument (pi4,pi400,cm4) tells the script to discard files which are not required by that product. This makes the image smaller and reduces the time taken to calculate the hash of the image file thereby reducing the boot time.
+The `-b` product argument (pi4,pi400,cm4) tells the script to discard files which are not required by that product. This makes the image smaller and reduces the time taken to calculate the hash of the image file thereby reducing the boot time.
 ```bash
 sudo ../tools/make-boot-image -d secure-boot-files -o boot.img -b pi4
 ```