diff --git a/app/app.go b/app/app.go
index b17634e..a136a4a 100644
--- a/app/app.go
+++ b/app/app.go
@@ -12,6 +12,9 @@ import (
 	"dnsupdater/ip/resolver"
 )
 
+// Constant name for the virtual WAN interface
+const WAN_IFACE = "wan"
+
 type App struct {
 	cache *ip.Cache
 
@@ -23,7 +26,7 @@ type App struct {
 
 func makeCacheCallback(service resolver.Service) ip.CacheDefaultCallback {
 	return func(name string) (net.IP, error) {
-		if name == resolver.WAN_IFACE {
+		if name == WAN_IFACE {
 			ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
 			defer cancel()
 			return service.Lookup(ctx)
diff --git a/ip/resolver/resolver.go b/ip/resolver/resolver.go
index 5e2c93a..094418f 100644
--- a/ip/resolver/resolver.go
+++ b/ip/resolver/resolver.go
@@ -13,6 +13,3 @@ type Service interface {
 	// Lookup the public ip.
 	Lookup(ctx context.Context) (net.IP, error)
 }
-
-// Constant name for the virtual WAN interface
-const WAN_IFACE = "wan"