diff --git a/sched/mqueue/mq_rcvinternal.c b/sched/mqueue/mq_rcvinternal.c
index 00ab85e373e..928a839ded7 100644
--- a/sched/mqueue/mq_rcvinternal.c
+++ b/sched/mqueue/mq_rcvinternal.c
@@ -187,6 +187,11 @@ int nxmq_wait_receive(mqd_t mqdes, FAR struct mqueue_msg_s **rcvmsg)
           saved_errno    = rtcb->pterrno;
           rtcb->pterrno  = OK;
 
+          /* Make sure this is not the idle task, descheduling that
+           * isn't going to end well.
+           */
+
+          DEBUGASSERT(NULL != rtcb->flink);
           up_block_task(rtcb, TSTATE_WAIT_MQNOTEMPTY);
 
           /* When we resume at this point, either (1) the message queue
diff --git a/sched/mqueue/mq_sndinternal.c b/sched/mqueue/mq_sndinternal.c
index af43976b159..072248a6822 100644
--- a/sched/mqueue/mq_sndinternal.c
+++ b/sched/mqueue/mq_sndinternal.c
@@ -291,6 +291,11 @@ int nxmq_wait_send(mqd_t mqdes)
               saved_errno   = rtcb->pterrno;
               rtcb->pterrno = OK;
 
+              /* Make sure this is not the idle task, descheduling that
+               * isn't going to end well.
+               */
+
+              DEBUGASSERT(NULL != rtcb->flink);
               up_block_task(rtcb, TSTATE_WAIT_MQNOTFULL);
 
               /* When we resume at this point, either (1) the message queue
diff --git a/sched/paging/pg_miss.c b/sched/paging/pg_miss.c
index 75beda6827b..f8841d46810 100644
--- a/sched/paging/pg_miss.c
+++ b/sched/paging/pg_miss.c
@@ -142,8 +142,12 @@ void pg_miss(void)
    *   to the next highest priority task.
    * - The blocked task will be marked with state TSTATE_WAIT_PAGEFILL
    *   and will be retained in the g_waitingforfill prioritized task list.
+   *
+   * Need to firstly check that this is not the idle task,descheduling
+   * that isn't going to end well.
    */
 
+  DEBUGASSERT(NULL != ftcb->flink);
   up_block_task(ftcb, TSTATE_WAIT_PAGEFILL);
 
   /* Boost the page fill worker thread priority.
diff --git a/sched/sched/sched_suspend.c b/sched/sched/sched_suspend.c
index eb9c580f581..e38c2cd9f8d 100644
--- a/sched/sched/sched_suspend.c
+++ b/sched/sched/sched_suspend.c
@@ -95,8 +95,11 @@ void sched_suspend(FAR struct tcb_s *tcb)
       /* The task was running or runnable before being stopped.  Simply
        * block it in the stopped state.  If tcb refers to this task, then
        * this action will block this task.
+       * Before doing that make sure this is not the idle task,
+       * descheduling that isn't going to end well.
        */
 
+      DEBUGASSERT(NULL != tcb->flink);
       up_block_task(tcb, TSTATE_TASK_STOPPED);
     }
 
diff --git a/sched/semaphore/sem_wait.c b/sched/semaphore/sem_wait.c
index 96adcdd6f8c..d43fd7bbbfe 100644
--- a/sched/semaphore/sem_wait.c
+++ b/sched/semaphore/sem_wait.c
@@ -163,8 +163,12 @@ int nxsem_wait(FAR sem_t *sem)
           saved_errno   = rtcb->pterrno;
           rtcb->pterrno = OK;
 
-          /* Add the TCB to the prioritized semaphore wait queue */
+          /* Add the TCB to the prioritized semaphore wait queue, after
+           * checking this is not the idle task - descheduling that
+           * isn't going to end well.
+           */
 
+          DEBUGASSERT(NULL != rtcb->flink);
           up_block_task(rtcb, TSTATE_WAIT_SEM);
 
           /* When we resume at this point, either (1) the semaphore has been
diff --git a/sched/signal/sig_suspend.c b/sched/signal/sig_suspend.c
index a4f5ebdf682..ade7da33b24 100644
--- a/sched/signal/sig_suspend.c
+++ b/sched/signal/sig_suspend.c
@@ -132,8 +132,12 @@ int sigsuspend(FAR const sigset_t *set)
     }
   else
     {
-      /* Its time to wait until one of the unblocked signals is posted */
+      /* Its time to wait until one of the unblocked signals is posted,
+       * but first, ensure this is not the idle task, descheduling that
+       * isn't going to end well.
+       */
 
+      DEBUGASSERT(NULL != rtcb->flink);
       up_block_task(rtcb, TSTATE_WAIT_SIG);
 
       /* We are running again, restore the original sigprocmask */
diff --git a/sched/signal/sig_timedwait.c b/sched/signal/sig_timedwait.c
index cdd6c9536fb..541d7a8aee2 100644
--- a/sched/signal/sig_timedwait.c
+++ b/sched/signal/sig_timedwait.c
@@ -357,8 +357,12 @@ int nxsig_timedwait(FAR const sigset_t *set, FAR struct siginfo *info,
               (void)wd_start(rtcb->waitdog, waitticks,
                              (wdentry_t)nxsig_timeout, 1, wdparm.pvarg);
 
-              /* Now wait for either the signal or the watchdog */
+              /* Now wait for either the signal or the watchdog, but
+               * first, make sure this is not the idle task,
+               * descheduling that isn't going to end well.
+               */
 
+              DEBUGASSERT(NULL != rtcb->flink);
               up_block_task(rtcb, TSTATE_WAIT_SIG);
 
               /* We no longer need the watchdog */
@@ -376,8 +380,12 @@ int nxsig_timedwait(FAR const sigset_t *set, FAR struct siginfo *info,
 
       else
         {
-          /* And wait until one of the unblocked signals is posted */
+          /* And wait until one of the unblocked signals is posted,
+           * but first make sure this is not the idle task,
+           * descheduling that isn't going to end well.
+           */
 
+          DEBUGASSERT(NULL != rtcb->flink);
           up_block_task(rtcb, TSTATE_WAIT_SIG);
         }