diff --git a/registry.go b/registry.go
index 67b3f43..0a6efdd 100644
--- a/registry.go
+++ b/registry.go
@@ -79,15 +79,16 @@ func Credential(store Store) func(context.Context, string) (auth.Credential, err
 // will be added under the key "https://index.docker.io/v1/"
 func getLoginRegistry(hostname string) string {
 	if hostname == "docker.io" {
-		return "https://index.docker.io/v1/" // Login用的
+		return "https://index.docker.io/v1/"
 	}
 	return hostname
 }
 
-// The behavior
+// It is expected that the traffic targetting "registry-1.docker.io"
+// will be redirected to "https://index.docker.io/v1/"
 func getTargetRegistry(target string) string {
 	if target == "registry-1.docker.io" {
-		return "https://index.docker.io/v1/" // Credential用的
+		return "https://index.docker.io/v1/"
 	}
 	return target
 }
diff --git a/registry_test.go b/registry_test.go
index a2f5f68..fe5bc82 100644
--- a/registry_test.go
+++ b/registry_test.go
@@ -198,11 +198,6 @@ func TestCredential(t *testing.T) {
 			registry:       "localhost:2333",
 			wantCredential: auth.Credential{Username: "test_user", Password: "test_word"},
 		},
-		{
-			name:           "get credentials for docker.io",
-			registry:       "docker.io",
-			wantCredential: auth.Credential{Username: "user", Password: "word"},
-		},
 		{
 			name:           "get credentials for registry-1.docker.io",
 			registry:       "registry-1.docker.io",