diff --git a/configure.ac b/configure.ac
index 220124a..3dba3b3 100755
--- a/configure.ac
+++ b/configure.ac
@@ -442,7 +442,7 @@
 dnl -------------------------
 AC_CHECK_HEADERS([stropts.h sys/ksym.h sys/times.h sys/select.h \
 	sys/types.h linux/version.h netdb.h asm/types.h \
-	sys/param.h limits.h signal.h \
+	sys/cdefs.h sys/param.h limits.h signal.h \
 	sys/socket.h netinet/in.h time.h sys/time.h])
 
 dnl Utility macro to avoid retyping includes all the time
diff --git a/isisd/include-netbsd/iso.h b/isisd/include-netbsd/iso.h
index 1a80aec..42b9bc8 100644
--- a/isisd/include-netbsd/iso.h
+++ b/isisd/include-netbsd/iso.h
@@ -192,7 +192,7 @@
 #else
 /* user utilities definitions from the iso library */
 
-#ifdef SUNOS_5
+#ifndef HAVE_SYS_CDEFS_H
 #define	__P(x)	x
 #define	__BEGIN_DECLS
 #define	__END_DECLS
diff --git a/lib/queue.h b/lib/queue.h
index 70cffab..48b363e 100644
--- a/lib/queue.h
+++ b/lib/queue.h
@@ -33,8 +33,6 @@
 #ifndef _SYS_QUEUE_H_
 #define	_SYS_QUEUE_H_
 
-#include <sys/cdefs.h>
-
 /*
  * This file defines four types of data structures: singly-linked lists,
  * singly-linked tail queues, lists and tail queues.