diff --git a/doc/board/kontron/sl-mx8mm.rst b/doc/board/kontron/sl-mx8mm.rst
index 57143b9..ff6f01d 100644
--- a/doc/board/kontron/sl-mx8mm.rst
+++ b/doc/board/kontron/sl-mx8mm.rst
@@ -20,6 +20,12 @@
 - Build U-Boot
 - Boot
 
+.. note::
+
+   To build on a x86-64 host machine, you need a GNU cross toolchain for the
+   target architecture (aarch64). Check your distros package manager or
+   download and install the necessary tools (``aarch64-linux-gnu-*``) manually.
+
 Get and Build the Trusted Firmware-A (TF-A)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^