diff --git a/sched/semaphore/sem_post.c b/sched/semaphore/sem_post.c
index 97235de428..c985ceb9c4 100644
--- a/sched/semaphore/sem_post.c
+++ b/sched/semaphore/sem_post.c
@@ -41,6 +41,7 @@
 
 #include <limits.h>
 #include <semaphore.h>
+#include <errno.h>
 #include <sched.h>
 
 #include <nuttx/irq.h>
@@ -157,6 +158,10 @@ int sem_post(FAR sem_t *sem)
 
       leave_critical_section(flags);
     }
+  else
+    {
+      set_errno(EINVAL);
+    }
 
   return ret;
 }
diff --git a/sched/semaphore/sem_wait.c b/sched/semaphore/sem_wait.c
index 86fb013696..49371e0ae6 100644
--- a/sched/semaphore/sem_wait.c
+++ b/sched/semaphore/sem_wait.c
@@ -86,9 +86,7 @@ int sem_wait(FAR sem_t *sem)
 
   DEBUGASSERT(up_interrupt_context() == false);
 
-  /* Assume any errors reported are due to invalid arguments. */
-
-  set_errno(EINVAL);
+  /* Make sure we were supplied with a valid semaphore. */
 
   if (sem)
     {
@@ -190,6 +188,10 @@ int sem_wait(FAR sem_t *sem)
 
       leave_critical_section(flags);
     }
+  else
+    {
+      set_errno(EINVAL);
+    }
 
   return ret;
 }