diff --git a/sys/sys/errno.h b/sys/sys/errno.h
index 52efd3193a0e..b6056d2f4cb0 100644
--- a/sys/sys/errno.h
+++ b/sys/sys/errno.h
@@ -184,7 +184,7 @@ __END_DECLS
 #define	ELAST		96		/* Must be equal largest errno */
 #endif /* _POSIX_SOURCE */
 
-#ifdef _KERNEL
+#if defined(_KERNEL) || defined(_WANT_KERNEL_ERRNO)
 /* pseudo-errors returned inside kernel to modify return to process */
 #define	ERESTART	(-1)		/* restart syscall */
 #define	EJUSTRETURN	(-2)		/* don't modify regs, just return */
diff --git a/usr.bin/kdump/kdump.c b/usr.bin/kdump/kdump.c
index 1ee1c84a9e5c..199ecdd53837 100644
--- a/usr.bin/kdump/kdump.c
+++ b/usr.bin/kdump/kdump.c
@@ -41,10 +41,7 @@ static char sccsid[] = "@(#)kdump.c	8.1 (Berkeley) 6/6/93";
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
-#define _KERNEL
-extern int errno;
-#include <sys/errno.h>
-#undef _KERNEL
+#define _WANT_KERNEL_ERRNO
 #include <sys/param.h>
 #include <sys/capsicum.h>
 #include <sys/errno.h>