--- a/sem.c
+++ b/sem.c
@@ -35,28 +35,12 @@
 #include <errno.h>
 #include "sem.h"
 
-/* If we've got a version of glibc that doesn't define union semun, we do
- * it ourseleves like in semctl(2). Otherwise, fall back to the original
- * buffer behaviour of defining it (differetly!) only on some systems.
- *
- * mbuck@debian.org, 1999/08/29
- */
-#if defined(__GNU_LIBRARY__) && defined(_SEM_SEMUN_UNDEFINED)
+// modern POSIX requires the user to provide this definition
 union semun {
 	int val;			/* value for SETVAL              */
 	struct semid_ds *buf;		/* buffer for IPC_STAT & IPC_SET */
 	unsigned short int *array;	/* array for GETALL & SETALL     */
-	struct seminfo *__buf;		/* buffer for IPC_INFO           */
 };
-#else
-#if defined(SYS5) || defined(ultrix) || defined(_AIX)
-union semun {
-	int val;
-	struct semid_ds *buf;
-	ushort *array;
-};
-#endif
-#endif
 
 /* IMPORTS */