diff --git a/unix/configure.ac b/unix/configure.ac
index 0cbd5cee..699e6ef8 100644
--- a/unix/configure.ac
+++ b/unix/configure.ac
@@ -14,7 +14,6 @@ if test "X$GCC" = Xyes; then
     CFLAGS="$CFLAGS -Wall -Werror"
 fi
 
-AC_CHECK_HEADERS([sys/sockio.h],,,[ ])
 AC_CHECK_HEADERS([utmpx.h],,,[
 #include <sys/types.h>
 #include <utmp.h>])
diff --git a/unix/uxnet.c b/unix/uxnet.c
index 5d4ace44..a43adcb1 100644
--- a/unix/uxnet.c
+++ b/unix/uxnet.c
@@ -23,7 +23,7 @@
 #include "tree234.h"
 
 /* Solaris needs <sys/sockio.h> for SIOCATMARK. */
-#ifdef HAVE_SYS_SOCKIO_H
+#ifndef SOCKATMARK
 #include <sys/sockio.h>
 #endif