diff --git a/sched/mqueue/mq_waitirq.c b/sched/mqueue/mq_waitirq.c
index 138d1ceccb..76d2e236d7 100644
--- a/sched/mqueue/mq_waitirq.c
+++ b/sched/mqueue/mq_waitirq.c
@@ -1,5 +1,5 @@
 /****************************************************************************
- *  sched/mqueue/mq_waitirq.c
+ * sched/mqueue/mq_waitirq.c
  *
  *   Copyright (C) 2007-2009, 2011, 2014 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
@@ -72,7 +72,7 @@
  ****************************************************************************/
 
 /****************************************************************************
- * Name: sem_waitirq
+ * Name: mq_waitirq
  *
  * Description:
  *   This function is called when a signal or a timeout is received by a
diff --git a/sched/semaphore/Make.defs b/sched/semaphore/Make.defs
index 5349d58b4d..44b7e21d06 100644
--- a/sched/semaphore/Make.defs
+++ b/sched/semaphore/Make.defs
@@ -34,11 +34,7 @@
 ############################################################################
 
 CSRCS += sem_destroy.c sem_wait.c sem_trywait.c sem_timedwait.c
-CSRCS += sem_post.c sem_recover.c
-
-ifneq ($(CONFIG_DISABLE_SIGNALS),y)
-CSRCS += sem_waitirq.c
-endif
+CSRCS += sem_post.c sem_recover.c sem_waitirq.c
 
 ifeq ($(CONFIG_PRIORITY_INHERITANCE),y)
 CSRCS += sem_initialize.c sem_holder.c
diff --git a/sched/semaphore/sem_waitirq.c b/sched/semaphore/sem_waitirq.c
index 49bed13ac7..5e9298f396 100644
--- a/sched/semaphore/sem_waitirq.c
+++ b/sched/semaphore/sem_waitirq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * sched/semaphore/sem_waitirq.c
  *
- *   Copyright (C) 2007-2010 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2010, 2014 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -46,7 +46,7 @@
 #include "semaphore/semaphore.h"
 
 /****************************************************************************
- * Definitions
+ * Pre-processor Definitions
  ****************************************************************************/
 
 /****************************************************************************
@@ -73,10 +73,14 @@
  * Name: sem_waitirq
  *
  * Description:
- *   This function is called when a signal is received by a task that is
- *   waiting on a semaphore.  According to the POSIX spec, "...the calling
- *   thread shall not return from the call to [sem_wait] until it either
- *   locks the semaphore or the call is interrupted by a signal."
+ *   This function is called when either:
+ *
+ *   1. A signal is received by a task that is waiting on a semaphore.
+ *      According to the POSIX spec, "...the calling thread shall not return
+ *      from the call to [sem_wait] until it either locks the semaphore or
+ *      the call is interrupted by a signal."
+ *   2. From logic associated with sem_timedwait().  This function is called
+ *      when the timeout elapses without receiving the semaphore.
  *
  * Parameters:
  *   wtcb    - A pointer to the TCB of the task that is waiting on a
@@ -142,4 +146,3 @@ void sem_waitirq(FAR struct tcb_s *wtcb, int errcode)
 
   irqrestore(saved_state);
 }
-