diff --git a/HACKING.md b/HACKING.md
index 51b99d98a31..b792e1ad8eb 100644
--- a/HACKING.md
+++ b/HACKING.md
@@ -1,6 +1,13 @@
 Hacking on Sky
 ==============
 
+Building
+--------
+
+* Follow the setup & build instructions for [mojo](https://github.com/domokit/mojo), except...
+  * run ``gn & ninja`` in ``<src>/sky/`` and use the build target ``sky`` with ``ninja`` rather than ``root`` or ``mojo``
+
+
 Running applications
 --------------------