diff --git a/lib/libc/gen/uexterr_gettext.c b/lib/libc/gen/uexterr_gettext.c
--- a/lib/libc/gen/uexterr_gettext.c
+++ b/lib/libc/gen/uexterr_gettext.c
@@ -8,7 +8,8 @@
  * under sponsorship from the FreeBSD Foundation.
  */
 
-#include <sys/types.h>
+#define	_WANT_P_OSREL
+#include <sys/param.h>
 #include <sys/exterrvar.h>
 #include <exterr.h>
 #include <string.h>
@@ -18,11 +19,14 @@
 	.ver = UEXTERROR_VER,
 };
 
+int __getosreldate(void);
+
 static void uexterr_ctr(void) __attribute__((constructor));
 static void
 uexterr_ctr(void)
 {
-	exterrctl(EXTERRCTL_ENABLE, 0, &uexterr);
+	if (__getosreldate() >= P_OSREL_EXTERRCTL)
+		exterrctl(EXTERRCTL_ENABLE, 0, &uexterr);
 }
 
 int
diff --git a/lib/libthr/thread/thr_create.c b/lib/libthr/thread/thr_create.c
--- a/lib/libthr/thread/thr_create.c
+++ b/lib/libthr/thread/thr_create.c
@@ -27,6 +27,7 @@
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#define _WANT_P_OSREL
 #include "namespace.h"
 #include <sys/types.h>
 #include <sys/rtprio.h>
@@ -44,6 +45,8 @@
 #include "libc_private.h"
 #include "thr_private.h"
 
+int __getosreldate(void);
+
 static int  create_stack(struct pthread_attr *pattr);
 static void thread_start(struct pthread *curthread);
 
@@ -287,7 +290,8 @@
 #endif
 
 	curthread->uexterr.ver = UEXTERROR_VER;
-	exterrctl(EXTERRCTL_ENABLE, 0, &curthread->uexterr);
+	if (__getosreldate() >= P_OSREL_EXTERRCTL)
+		exterrctl(EXTERRCTL_ENABLE, 0, &curthread->uexterr);
 
 	/* Run the current thread's start routine with argument: */
 	_pthread_exit(curthread->start_routine(curthread->arg));
diff --git a/lib/libthr/thread/thr_init.c b/lib/libthr/thread/thr_init.c
--- a/lib/libthr/thread/thr_init.c
+++ b/lib/libthr/thread/thr_init.c
@@ -33,6 +33,7 @@
  * SUCH DAMAGE.
  */
 
+#define _WANT_P_OSREL
 #include "namespace.h"
 #include <sys/param.h>
 #include <sys/auxv.h>
@@ -59,6 +60,7 @@
 #include "libc_private.h"
 #include "thr_private.h"
 
+int		__getosreldate(void);
 char		*_usrstack;
 struct pthread	*_thr_initial;
 int		_libthr_debug;
@@ -434,7 +436,8 @@
 #endif
 
 	thread->uexterr.ver = UEXTERROR_VER;
-	exterrctl(EXTERRCTL_ENABLE, EXTERRCTLF_FORCE, &thread->uexterr);
+	if (__getosreldate() >= P_OSREL_EXTERRCTL)
+		exterrctl(EXTERRCTL_ENABLE, EXTERRCTLF_FORCE, &thread->uexterr);
 
 	/* Others cleared to zero by thr_alloc() */
 }