diff --git a/configs/b-l475e-iot01a/README.txt b/configs/b-l475e-iot01a/README.txt
index e99c3a9503..013ac41fbf 100644
--- a/configs/b-l475e-iot01a/README.txt
+++ b/configs/b-l475e-iot01a/README.txt
@@ -27,6 +27,9 @@ STATUS
     NuttX.  But no work has yet been done for this board port other
     than writing this README file.
 
+  o 2017-06-13:  I just learned that development boards will not be
+    available for another month.
+
 Board Features
 ==============
 
diff --git a/include/sys/syscall.h b/include/sys/syscall.h
index 6f1911c6c4..3f21f74d73 100644
--- a/include/sys/syscall.h
+++ b/include/sys/syscall.h
@@ -430,8 +430,7 @@
 #  define SYS_pthread_setschedparam    (__SYS_pthread_once+1)
 #  define SYS_pthread_setschedprio     (__SYS_pthread_once+2)
 #  define SYS_pthread_setspecific      (__SYS_pthread_once+3)
-#  define SYS_pthread_yield            (__SYS_pthread_once+4)
-#  define __SYS_pthread_smp            (__SYS_pthread_once+5)
+#  define __SYS_pthread_smp            (__SYS_pthread_once+4)
 
 #  ifdef CONFIG_SMP
 #    define SYS_pthread_setaffinity_np (__SYS_pthread_smp+0)
diff --git a/libc/libc.csv b/libc/libc.csv
index 02cf739bd3..89bc65c0b0 100644
--- a/libc/libc.csv
+++ b/libc/libc.csv
@@ -117,6 +117,7 @@
 "pthread_mutexattr_init","pthread.h","!defined(CONFIG_DISABLE_PTHREAD)","int","FAR pthread_mutexattr_t *"
 "pthread_mutexattr_setpshared","pthread.h","!defined(CONFIG_DISABLE_PTHREAD)","int","FAR pthread_mutexattr_t *","int "
 "pthread_mutexattr_settype","pthread.h","!defined(CONFIG_DISABLE_PTHREAD) && defined(CONFIG_PTHREAD_MUTEX_TYPES)","int","pthread_mutexattr_t *","int"
+"pthread_yield","pthread.h","!defined(CONFIG_DISABLE_PTHREAD)","void"
 "puts","stdio.h","CONFIG_NFILE_DESCRIPTORS > 0 && CONFIG_NFILE_STREAMS > 0","int","FAR const char *"
 "qsort","stdlib.h","","void","void *","size_t","size_t","int(*)(const void *","FAR const void *)"
 "rand","stdlib.h","","int"
diff --git a/libc/pthread/Make.defs b/libc/pthread/Make.defs
index 291dfdfd4e..5cd35f0255 100644
--- a/libc/pthread/Make.defs
+++ b/libc/pthread/Make.defs
@@ -53,6 +53,7 @@ CSRCS += pthread_mutexattr_setrobust.c pthread_mutexattr_getrobust.c
 CSRCS += pthread_setcancelstate.c pthread_setcanceltype.c
 CSRCS += pthread_testcancel.c
 CSRCS += pthread_rwlock.c pthread_rwlock_rdlock.c pthread_rwlock_wrlock.c
+CSRCS += pthread_yield.c
 
 ifeq ($(CONFIG_SMP),y)
 CSRCS += pthread_attr_getaffinity.c pthread_attr_setaffinity.c
diff --git a/sched/pthread/pthread_yield.c b/libc/pthread/pthread_yield.c
similarity index 96%
rename from sched/pthread/pthread_yield.c
rename to libc/pthread/pthread_yield.c
index 0577e21f83..2af7ea2b93 100644
--- a/sched/pthread/pthread_yield.c
+++ b/libc/pthread/pthread_yield.c
@@ -1,7 +1,7 @@
 /****************************************************************************
- * sched/pthread/pthread_yield.c
+ * libc/pthread/pthread_yield.c
  *
- *   Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007, 2009, 2017 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/sched/pthread/Make.defs b/sched/pthread/Make.defs
index 20bc7e8d6c..4d7b870957 100644
--- a/sched/pthread/Make.defs
+++ b/sched/pthread/Make.defs
@@ -36,7 +36,7 @@
 ifneq ($(CONFIG_DISABLE_PTHREAD),y)
 
 CSRCS += pthread_create.c pthread_exit.c pthread_join.c pthread_detach.c
-CSRCS += pthread_yield.c pthread_getschedparam.c pthread_setschedparam.c
+CSRCS += pthread_getschedparam.c pthread_setschedparam.c
 CSRCS += pthread_mutexinit.c pthread_mutexdestroy.c
 CSRCS += pthread_mutexlock.c pthread_mutextrylock.c pthread_mutexunlock.c
 CSRCS += pthread_condinit.c pthread_conddestroy.c
diff --git a/syscall/syscall.csv b/syscall/syscall.csv
index 1ff6948d74..8afdd21caf 100644
--- a/syscall/syscall.csv
+++ b/syscall/syscall.csv
@@ -99,7 +99,6 @@
 "pthread_setschedprio","pthread.h","!defined(CONFIG_DISABLE_PTHREAD)","int","pthread_t","int"
 "pthread_setspecific","pthread.h","!defined(CONFIG_DISABLE_PTHREAD)","int","pthread_key_t","FAR const void*"
 "pthread_sigmask","pthread.h","!defined(CONFIG_DISABLE_SIGNALS) && !defined(CONFIG_DISABLE_PTHREAD)","int","int","FAR const sigset_t*","FAR sigset_t*"
-"pthread_yield","pthread.h","!defined(CONFIG_DISABLE_PTHREAD)","void"
 "putenv","stdlib.h","!defined(CONFIG_DISABLE_ENVIRON)","int","FAR const char*"
 "read","unistd.h","CONFIG_NSOCKET_DESCRIPTORS > 0 || CONFIG_NFILE_DESCRIPTORS > 0","ssize_t","int","FAR void*","size_t"
 "readdir","dirent.h","CONFIG_NFILE_DESCRIPTORS > 0","FAR struct dirent*","FAR DIR*"
diff --git a/syscall/syscall_lookup.h b/syscall/syscall_lookup.h
index 0719358487..4096ebabb9 100644
--- a/syscall/syscall_lookup.h
+++ b/syscall/syscall_lookup.h
@@ -310,7 +310,6 @@ SYSCALL_LOOKUP(up_assert,                  2, STUB_up_assert)
   SYSCALL_LOOKUP(pthread_setschedparam,    3, STUB_pthread_setschedparam)
   SYSCALL_LOOKUP(pthread_setschedprio,     2, STUB_pthread_setschedprio)
   SYSCALL_LOOKUP(pthread_setspecific,      2, STUB_pthread_setspecific)
-  SYSCALL_LOOKUP(pthread_yield,            0, STUB_pthread_yield)
 #  ifdef CONFIG_SMP
   SYSCALL_LOOKUP(pthread_setaffinity,      3, STUB_pthread_setaffinity)
   SYSCALL_LOOKUP(pthread_getaffinity,      3, STUB_pthread_getaffinity)
diff --git a/syscall/syscall_stublookup.c b/syscall/syscall_stublookup.c
index 2cc52ad0a3..20119fbfbf 100644
--- a/syscall/syscall_stublookup.c
+++ b/syscall/syscall_stublookup.c
@@ -310,7 +310,6 @@ uintptr_t STUB_pthread_setschedprio(int nbr, uintptr_t parm1,
             uintptr_t parm2);
 uintptr_t STUB_pthread_setspecific(int nbr, uintptr_t parm1,
             uintptr_t parm2);
-uintptr_t STUB_pthread_yield(int nbr);
 
 uintptr_t STUB_pthread_setaffinity(int nbr, uintptr_t parm1,
             uintptr_t parm2, uintptr_t parm3);