diff --git a/sched/init/nx_start.c b/sched/init/nx_start.c
index 7840387e7f9..33573a1741b 100644
--- a/sched/init/nx_start.c
+++ b/sched/init/nx_start.c
@@ -801,18 +801,21 @@ void nx_start(void)
   for (; ; )
     {
 #if defined(CONFIG_STACK_COLORATION) && defined(CONFIG_DEBUG_MM)
-      irqstate_t flags;
 
       /* Check stack in idle thread */
 
-      for (i = 0; i < CONFIG_MAX_TASKS && g_pidhash[i].tcb; i++)
+      for (i = 0; i < CONFIG_MAX_TASKS; i++)
         {
+          FAR struct tcb_s *tcb;
+          irqstate_t flags;
+
           flags = enter_critical_section();
 
-          if (up_check_tcbstack_remain(g_pidhash[i].tcb) <= 0)
+          tcb = g_pidhash[i].tcb;
+          if (tcb && up_check_tcbstack_remain(tcb) <= 0)
             {
               _alert("Stack check failed, pid %d, name %s\n",
-                      g_pidhash[i].tcb->pid, g_pidhash[i].tcb->name);
+                      tcb->pid, tcb->name);
               PANIC();
             }