diff --git a/readme.txt b/readme.txt
index 203a585bf..fa9beaad9 100644
--- a/readme.txt
+++ b/readme.txt
@@ -80,8 +80,9 @@ Win32-MinGW            - ChibiOS/RT simulator and demo into a WIN32 process,
 - FIX: Fixed a regression introduced in version 0.6.9, the queues benchmark
   test case was missing from the tests list.
 - NEW: Added an option to the ARM7 ports, by specifying -DREENTRANT_LOCKS in
-  the makefile options the chSysLock() and chSysUnlock() become reentrant.
-  The code becomes a bit larger and slower.
+  the makefile options makes the chSysLock() and chSysUnlock() become
+  reentrant. The code becomes a bit larger and slower, use it only if your
+  application really needs to invoke system API under lock.
 
 *** 0.6.9 ***
 - NEW: Added an option to exclude the support for the round robin scheduling,