Index: dnstop.c
--- dnstop.c.orig
+++ dnstop.c
@@ -48,6 +48,7 @@ static const char *Version = "@VERSION@";
 #include <netdb.h>
 
 #ifdef HAVE_NET_IF_PPP_H
+#include <net/ppp_defs.h>
 #include <net/if_ppp.h>
 #define PPP_ADDRESS_VAL       0xff	/* The address byte value */
 #define PPP_CONTROL_VAL       0x03	/* The control byte value */
