diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index 699b79d..08343e3 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -149,6 +149,12 @@
    (RAM) or 1 (non-volatile memory like flash) as test results storage. Default
    value is 0, as writing to the flash significantly slows tests down.
 
+Cactus SP Build Options
+-----------------------
+
+- ``SPMC_AT_EL3``: This flag is required to match the feature set of Cactus SP that
+   are implemented in TF-A EL3 SPMC. Default value is 0.
+
 Realm payload specific Build Options
 ------------------------------------