diff --git a/lib/libsys/Makefile b/lib/libsys/Makefile
--- a/lib/libsys/Makefile
+++ b/lib/libsys/Makefile
@@ -25,6 +25,8 @@
 
 INCS=	libsys.h _libsys.h
 
+CFLAGS+=-DLIBSYS
+
 CFLAGS+=-I${LIBSYS_SRCTOP}/include -I${LIBC_SRCTOP}/include
 CFLAGS+=-I${LIBSYS_SRCTOP}/${LIBC_ARCH}
 CFLAGS+=-I${LIBC_SRCTOP}/${LIBC_ARCH}
diff --git a/lib/libsys/Symbol.map b/lib/libsys/Symbol.map
--- a/lib/libsys/Symbol.map
+++ b/lib/libsys/Symbol.map
@@ -1,5 +1,6 @@
 FBSDprivate_1.0 {
 	__elf_aux_vector;
+	__libsys_errno;
 	__getosreldate;
 	__libsys_interposing_slot;
 	__realpathat;
diff --git a/lib/libsys/Symbol.sys.map b/lib/libsys/Symbol.sys.map
--- a/lib/libsys/Symbol.sys.map
+++ b/lib/libsys/Symbol.sys.map
@@ -72,7 +72,6 @@
 	extattr_set_file;
 	extattr_set_link;
 	extattrctl;
-	errno;
 	fchdir;
 	fchflags;
 	fchmod;
diff --git a/lib/libsys/__error.c b/lib/libsys/__error.c
--- a/lib/libsys/__error.c
+++ b/lib/libsys/__error.c
@@ -31,13 +31,15 @@
 
 #include "libc_private.h"
 
-int errno;
+int __libsys_errno;
+#ifdef LIBSYS
+__sym_compat(errno, __libsys_errno, FBSD_1.0);
+#endif
 
 static int *
 __error_unthreaded(void)
 {
-
-	return (&errno);
+	return (&__libsys_errno);
 }
 
 static int *(*__error_selector)(void) = __error_unthreaded;
@@ -45,13 +47,11 @@
 void
 __set_error_selector(int *(*arg)(void))
 {
-
 	__error_selector = arg;
 }
 
 int *
 __error(void)
 {
-
 	return (__error_selector());
 }
diff --git a/lib/libthr/sys/thr_error.c b/lib/libthr/sys/thr_error.c
--- a/lib/libthr/sys/thr_error.c
+++ b/lib/libthr/sys/thr_error.c
@@ -39,8 +39,7 @@
 #include "libc_private.h"
 #include "thr_private.h"
 
-#undef errno
-extern	int	errno;
+extern	int	__libsys_errno;
 
 __weak_reference(__error_threaded, __error);
 int *
@@ -53,5 +52,5 @@
 		if (curthread != NULL && curthread != _thr_initial)
 			return (&curthread->error);
 	}
-	return (&errno);
+	return (&__libsys_errno);
 }
diff --git a/lib/libthr/thread/thr_rtld.c b/lib/libthr/thread/thr_rtld.c
--- a/lib/libthr/thread/thr_rtld.c
+++ b/lib/libthr/thread/thr_rtld.c
@@ -39,8 +39,7 @@
 #include "rtld_lock.h"
 #include "thr_private.h"
 
-#undef errno
-extern int errno;
+extern int __libsys_errno;
 
 static int	_thr_rtld_clr_flag(int);
 static void	*_thr_rtld_lock_create(void);
@@ -96,14 +95,14 @@
 	if (curthread != _thr_initial)		\
 		errsave = curthread->error;	\
 	else					\
-		errsave = errno;		\
+		errsave = __libsys_errno;	\
 }
 
 #define RESTORE_ERRNO()	{ 			\
 	if (curthread != _thr_initial)  	\
 		curthread->error = errsave;	\
 	else					\
-		errno = errsave;		\
+		__libsys_errno = errsave;	\
 }
 
 static void