diff --git a/sched/pthread/pthread_mutexlock.c b/sched/pthread/pthread_mutexlock.c
index 251f071b474..c39a384bed4 100644
--- a/sched/pthread/pthread_mutexlock.c
+++ b/sched/pthread/pthread_mutexlock.c
@@ -170,6 +170,7 @@ int pthread_mutex_lock(FAR pthread_mutex_t *mutex)
       else if (mutex->pid > 0 && sched_gettcb(mutex->pid) == NULL)
         {
           DEBUGASSERT(mutex->pid != 0); /* < 0: available, >0 owned, ==0 error */
+          DEBUGASSERT((mutex->flags & _PTHREAD_MFLAGS_INCONSISTENT) != 0);
 
           /* A thread holds the mutex, but there is no such thread.  POSIX
            * requires that the 'robust' mutex return EOWNERDEAD in this case.
@@ -177,7 +178,8 @@ int pthread_mutex_lock(FAR pthread_mutex_t *mutex)
            * fo fix the mutex.
            */
 
-          ret = EOWNERDEAD;
+          mutex->flags |= _PTHREAD_MFLAGS_INCONSISTENT;
+          ret           = EOWNERDEAD;
         }
       else
         {
diff --git a/sched/pthread/pthread_mutextrylock.c b/sched/pthread/pthread_mutextrylock.c
index 630de9e5fd3..683909c8594 100644
--- a/sched/pthread/pthread_mutextrylock.c
+++ b/sched/pthread/pthread_mutextrylock.c
@@ -157,6 +157,7 @@ int pthread_mutex_trylock(FAR pthread_mutex_t *mutex)
               if (mutex->pid > 0 && sched_gettcb(mutex->pid) == NULL)
                 {
                   DEBUGASSERT(mutex->pid != 0); /* < 0: available, >0 owned, ==0 error */
+                  DEBUGASSERT((mutex->flags & _PTHREAD_MFLAGS_INCONSISTENT) != 0);
 
                   /* A thread holds the mutex, but there is no such thread. 
                    * POSIX requires that the 'robust' mutex return EOWNERDEAD
@@ -164,7 +165,8 @@ int pthread_mutex_trylock(FAR pthread_mutex_t *mutex)
                    * call pthread_mutx_consistent() fo fix the mutex.
                    */
 
-                  ret = EOWNERDEAD;
+                  mutex->flags |= _PTHREAD_MFLAGS_INCONSISTENT;
+                  ret           = EOWNERDEAD;
                 }
 
               /* The mutex is locked by another, active thread */