diff --git a/meta/recipes-rt/README b/meta/recipes-rt/README
index 7d7558de49..0144d68b70 100644
--- a/meta/recipes-rt/README
+++ b/meta/recipes-rt/README
@@ -10,4 +10,4 @@ If you are creating a new BSP which should use linux-yocto-rt by default,
 use the line above in the $MACHINE.conf in your BSP layer, and specify the
 following in a linux-yocto-rt bbappend recipe:
 
-COMPATIBLE_MACHINE_$MACHINE = $MACHINE
+COMPATIBLE_MACHINE:$MACHINE = $MACHINE