diff --git a/c/src/lib/libbsp/shared/ChangeLog b/c/src/lib/libbsp/shared/ChangeLog
index 23504f6e1a..1ac7dca1fa 100644
--- a/c/src/lib/libbsp/shared/ChangeLog
+++ b/c/src/lib/libbsp/shared/ChangeLog
@@ -1,3 +1,10 @@
+2008-10-13	Joel Sherrill <joel.sherrill@oarcorp.com>
+
+	* clock_driver_simidle.c: Ensure ISR nest level and Thread Dispatch
+	disable level are in the same state they would be in a true ISR. This
+	ensures that all of the clock tick handling is as similar as possible
+	in this limited environment.
+
 2008-10-02	Joel Sherrill <joel.sherrill@OARcorp.com>
 
 	* include/tm27.h: Use shared tm27.h stub.
diff --git a/c/src/lib/libbsp/shared/clock_driver_simidle.c b/c/src/lib/libbsp/shared/clock_driver_simidle.c
index 6d174bff65..39a82c08ff 100644
--- a/c/src/lib/libbsp/shared/clock_driver_simidle.c
+++ b/c/src/lib/libbsp/shared/clock_driver_simidle.c
@@ -7,7 +7,9 @@
  *  $Id$
  */
 
+#define __RTEMS_VIOLATE_KERNEL_VISIBILITY__
 #include <rtems.h>
+#include <rtems/score/thread.h>
 
 #define CLOCK_VECTOR 0
 
@@ -40,8 +42,13 @@ Thread clock_driver_sim_idle_body(
 )
 {
   for( ; ; ) {
-    if ( clock_driver_enabled )
-      rtems_clock_tick();
+    if ( clock_driver_enabled ) {
+      _Thread_Disable_dispatch();
+      _ISR_Nest_level++;
+	rtems_clock_tick();
+      _ISR_Nest_level--;
+      _Thread_Enable_dispatch();
+    }
   }
   return 0;   /* to avoid warning */
 }