diff --git a/ip/ipmonitor.c b/ip/ipmonitor.c
index 9d5ac2b5..743632cc 100644
--- a/ip/ipmonitor.c
+++ b/ip/ipmonitor.c
@@ -24,7 +24,7 @@
 #include "ip_common.h"
 
 static void usage(void) __attribute__((noreturn));
-int prefix_banner;
+static int prefix_banner;
 int listen_all_nsid;
 
 static void usage(void)