diff --git a/configure.in b/configure.in
index c081c229..7252d06e 100644
--- a/configure.in
+++ b/configure.in
@@ -14,16 +14,14 @@ AC_AIX
 AC_ISC_POSIX
 AC_MINIX
 AC_STDC_HEADERS
-AC_UNISTD_H
 AC_DIR_HEADER
 AC_UID_T			dnl Also does gid_t.
 AC_GETGROUPS_T
 AC_PID_T
 AC_RETSIGTYPE
-AC_HAVE_HEADERS(limits.h sys/param.h fcntl.h string.h memory.h)
+AC_HAVE_HEADERS(unistd.h limits.h sys/param.h fcntl.h string.h memory.h)
 AC_MINUS_C_MINUS_O
 AC_CONST			dnl getopt needs this.
-AC_USG
 AC_STAT_MACROS_BROKEN
 
 AC_SUBST(LIBOBJS)