diff --git a/lib/libc/net/Makefile.inc b/lib/libc/net/Makefile.inc
index 953e961dc..e8db73446 100644
--- a/lib/libc/net/Makefile.inc
+++ b/lib/libc/net/Makefile.inc
@@ -4,6 +4,10 @@
 # net sources
 .if defined(__MINIX)
 .PATH: ${.CURDIR}/net/minix
+
+CPPFLAGS.getpeereid.c+= -D_MINIX_SYSTEM=1
+CPPFLAGS.getsockopt.c+= -D_MINIX_SYSTEM=1
+CPPFLAGS.setsockopt.c+= -D_MINIX_SYSTEM=1
 .endif
 .PATH: ${ARCHDIR}/net ${.CURDIR}/net
 
diff --git a/sys/sys/socket.h b/sys/sys/socket.h
index cfea65855..e910d1656 100644
--- a/sys/sys/socket.h
+++ b/sys/sys/socket.h
@@ -131,7 +131,8 @@ typedef	_BSD_SSIZE_T_	ssize_t;
 #define	SO_ACCEPTFILTER	0x1000		/* there is an accept filter */
 #define	SO_TIMESTAMP	0x2000		/* timestamp received dgram traffic */
 
-#if defined(__minix)
+#if defined(__minix) && defined(_MINIX_SYSTEM)
+/* Minixism which should go, so hide it from userland. */
 #define SO_PASSCRED    0x100000
 #define SO_PEERCRED    0x200000
 #endif /* defined(__minix) */
diff --git a/test/Makefile b/test/Makefile
index 80e59d494..410c5b798 100644
--- a/test/Makefile
+++ b/test/Makefile
@@ -26,6 +26,8 @@ COPTS.test51.c=	-mhard-float
 COPTS.test52.c=	-mhard-float
 .endif
 
+CPPFLAGS.test56.c += -D_MINIX_SYSTEM=1
+
 WARNS=
 COPTS.test9.c=	-O0
 COPTS.test37.c=	-O0