diff --git a/docs/design/firmware-design.rst b/docs/design/firmware-design.rst
index 4958fc0..4e380bf 100644
--- a/docs/design/firmware-design.rst
+++ b/docs/design/firmware-design.rst
@@ -978,8 +978,8 @@
 framework finally sets up the execution stack for the handler, and invokes the
 services ``handle()`` function.
 
-On return from the handler the result registers are populated in X0-X3 before
-restoring the stack and CPU state and returning from the original SMC.
+On return from the handler the result registers are populated in X0-X7 as needed
+before restoring the stack and CPU state and returning from the original SMC.
 
 Exception Handling Framework
 ----------------------------