diff --git a/src/s/usg5-4.h b/src/s/usg5-4.h
index 70fb8ccb74d..6a28e8e9c54 100644
--- a/src/s/usg5-4.h
+++ b/src/s/usg5-4.h
@@ -57,13 +57,6 @@ Boston, MA 02111-1307, USA.  */
 /* there are no -lg libraries on this system, and no libPW */
 
 #define LIBS_DEBUG
-/* This is turned off because nobody actually uses LIBS_STANDARD (Nov 1995).
-   That name is a typo.  The next step is to delete this entirely.  */
-/* #define LIBS_STANDARD -lc */
-
-/* No <sioctl.h> */
-
-#define NO_SIOCTL_H
 
 /* Undump with ELF */
 
@@ -135,9 +128,7 @@ Boston, MA 02111-1307, USA.  */
    subprocesses the usual way.  But TIOCSIGNAL does work for PTYs, and
    this is all we need.  */
 
-#ifndef IRIX6
 #define TIOCSIGSEND TIOCSIGNAL
-#endif
 
 /* This change means that we don't loop through allocate_pty too many
    times in the (rare) event of a failure. */
@@ -198,9 +189,13 @@ Boston, MA 02111-1307, USA.  */
    So give it a try.  */
 #define HAVE_SOCKETS
 
+#ifndef HAVE_BCOPY
 #define bcopy(src,dst,n)	memmove (dst,src,n)
-#define bcmp(src,dst,n)		memcmp (src,dst,n)
 #define bzero(s,n)		memset (s,0,n)
+#endif
+#ifdef HAVE_BCMP
+#define bcmp(src,dst,n)		memcmp (src,dst,n)
+#endif
 
 /* Markus Weiand <weiand@khof.com> says this is needed for Motif on
    SINIX.  */