diff --git a/docs/getting_started/porting-guide.rst b/docs/getting_started/porting-guide.rst
index 7f38054..aa57e1d 100644
--- a/docs/getting_started/porting-guide.rst
+++ b/docs/getting_started/porting-guide.rst
@@ -1502,8 +1502,8 @@
 - This function indicates whether cache management operations should be
   performed. It returns 0 if CMOs should be skipped and non-zero
   otherwise.
-- The function must not clobber x2 and x3. It's also not safe to rely on stack.
-  Otherwise obey AAPCS.
+- The function must not clobber x1, x2 and x3. It's also not safe to rely on
+  stack. Otherwise obey AAPCS.
 
 Modifications specific to a Boot Loader stage
 ---------------------------------------------