--- a/fping.c
+++ b/fping.c
@@ -106,6 +106,7 @@
 
 #include <arpa/inet.h>
 #include <netdb.h>
+#include <err.h> /* err() warnx() */
 
 /* RS6000 has sys/select.h */
 #ifdef HAVE_SYS_SELECT_H