diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index 57b880a..15535d4 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -781,6 +781,11 @@
   feature for AArch64. The default is 0 and it is automatically disabled when
   the target architecture is AArch32.
 
+- ``ENABLE_SYS_REG_TRACE_FOR_NS``: Boolean option to enable trace system
+  registers access from NS ELs, NS-EL2 or NS-EL1 (when NS-EL2 is implemented
+  but unused). This feature is available if trace unit such as ETMv4.x, and
+  ETE(extending ETM feature) is implemented. This flag is disabled by default.
+
 GICv3 driver options
 --------------------