diff --git a/configure.ac b/configure.ac
index e86aedf0..a2adac1e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -81,6 +81,7 @@ AC_CHECK_HEADERS([ \
 libutil.h \
 linux/if_tun.h \
 mach/mach.h \
+net/if_ppp.h \
 pty.h \
 semaphore.h \
 util.h \
diff --git a/src/io.c b/src/io.c
index 219284bf..f39dbeb6 100644
--- a/src/io.c
+++ b/src/io.c
@@ -35,14 +35,22 @@
 #include <unistd.h>
 #include <arpa/inet.h>
 #include <netinet/tcp.h>
-#include <net/if_ppp.h>
 #include <sys/ioctl.h>
 
-
 #include <errno.h>
 #include <signal.h>
 #include <string.h>
 
+#if !HAVE_NET_IF_PPP_H
+#include <net/if_ppp.h>
+#else
+#define PPP_IP		0x21	/* Internet Protocol */
+#define PPP_IPV6	0x57	/* Internet Protocol Version 6 */
+#define PPP_IPCP	0x8021	/* IP Control Protocol */
+#define PPP_LCP		0xc021	/* Link Control Protocol */
+#define PPP_CHAP	0xc223	/* Cryptographic Handshake Auth. Protocol */
+#endif
+
 #if HAVE_MACH_MACH_H
 /* this is typical for mach kernel used on Mac OS X */
 #include <mach/mach.h>