diff --git a/os/rt/src/chstats.c b/os/rt/src/chstats.c
index 40169642e..82d2a67a1 100644
--- a/os/rt/src/chstats.c
+++ b/os/rt/src/chstats.c
@@ -72,7 +72,9 @@ void _stats_init(void) {
  */
 void _stats_increase_irq(void) {
 
+  port_lock_from_isr();
   ch.kernel_stats.n_irq++;
+  port_unlock_from_isr();
 }
 
 /**
diff --git a/readme.txt b/readme.txt
index 7a4c9481d..29afe7a02 100644
--- a/readme.txt
+++ b/readme.txt
@@ -76,6 +76,8 @@
 - RT:  Removed the p_msg field from the thread_t structure saving a
        msg_t-sized field from the structure. Messages now use a new field
        into the p_u union. Now synchronous messages are even faster.
+- RT:  Fixed ISR statistics are not updated from a critical zone in RT
+       (bug #693)(backported to 3.0.5 and 16.1.1).
 - NIL: Fixed NIL test suite calls I and S functions outside critical zone
        (bug #692)(backported to 3.0.5 and 16.1.1).
 - NIL: Fixed protocol violation in NIL OSAL (bug #691)(backported to