diff --git a/example_test.go b/example_test.go
index 03ebeaa..6aaed3c 100644
--- a/example_test.go
+++ b/example_test.go
@@ -29,6 +29,10 @@
 	return fmt.Sprint(*i)
 }
 
+func (i *interval) Type() string {
+	return "interval"
+}
+
 // Set is the method to set the flag value, part of the flag.Value interface.
 // Set's argument is a string to be parsed to set the flag.
 // It's a comma-separated list, so we split it.
diff --git a/flag_test.go b/flag_test.go
index 4d95b15..47865bd 100644
--- a/flag_test.go
+++ b/flag_test.go
@@ -245,6 +245,10 @@
 	return nil
 }
 
+func (f *flagVar) Type() string {
+	return "flagVar"
+}
+
 func TestUserDefined(t *testing.T) {
 	var flags FlagSet
 	flags.Init("test", ContinueOnError)