diff --git a/armsrc/em4x70.h b/armsrc/em4x70.h
index 83a8237d7..541e1cf51 100644
--- a/armsrc/em4x70.h
+++ b/armsrc/em4x70.h
@@ -13,7 +13,7 @@
 //
 // See LICENSE.txt for the text of the license.
 //-----------------------------------------------------------------------------
-// Low frequency EM4x70 commands
+// Low frequency EM4x70 commands -- ARM source only (not client)
 //-----------------------------------------------------------------------------
 
 #ifndef EM4x70_H