diff --git a/mtr/net.c b/mtr/net.c
index bd7ee41..4c89185 100644
--- a/mtr/net.c
+++ b/mtr/net.c
@@ -201,6 +201,7 @@ extern int bitpattern;		/* packet bit pattern used by ping */
 extern int tos;			/* type of service set in ping packet*/
 extern int af;			/* address family of remote target */
 extern int mtrtype;		/* type of query packet used */
+ip_t unspec_addr;
 
 /* return the number of microseconds to wait before sending the next
    ping */
diff --git a/mtr/net.h b/mtr/net.h
index 6e2c172..bc6ca38 100644
--- a/mtr/net.h
+++ b/mtr/net.h
@@ -121,7 +121,7 @@ extern int fld_index[];
 extern unsigned char fld_active[];
 extern char available_options[];
 
-ip_t unspec_addr;
+extern ip_t unspec_addr;
 
 /* MPLS label object */
 struct mplslen {