diff --git a/bridge/fdb.c b/bridge/fdb.c
index 336cf9d7..cca99ef3 100644
--- a/bridge/fdb.c
+++ b/bridge/fdb.c
@@ -27,7 +27,7 @@
 #include "rt_names.h"
 #include "utils.h"
 
-int filter_index;
+static unsigned int filter_index;
 
 static void usage(void)
 {
diff --git a/bridge/link.c b/bridge/link.c
index e3fd6e63..90d9e7f5 100644
--- a/bridge/link.c
+++ b/bridge/link.c
@@ -15,7 +15,7 @@
 #include "utils.h"
 #include "br_common.h"
 
-unsigned int filter_index;
+static unsigned int filter_index;
 
 static const char *port_states[] = {
 	[BR_STATE_DISABLED] = "disabled",
diff --git a/bridge/mdb.c b/bridge/mdb.c
index 81d479b9..6c1c938a 100644
--- a/bridge/mdb.c
+++ b/bridge/mdb.c
@@ -24,7 +24,7 @@
 	((struct rtattr*)(((char*)(r)) + NLMSG_ALIGN(sizeof(struct br_port_msg))))
 #endif
 
-int filter_index;
+static unsigned int filter_index;
 
 static void usage(void)
 {
diff --git a/bridge/vlan.c b/bridge/vlan.c
index 83c40880..3bd7b0db 100644
--- a/bridge/vlan.c
+++ b/bridge/vlan.c
@@ -13,7 +13,7 @@
 #include "br_common.h"
 #include "utils.h"
 
-int filter_index;
+static unsigned int filter_index;
 
 static void usage(void)
 {