diff --git a/extensions/envoyproxy_validate/envoyproxy_validate.go b/extensions/envoyproxy_validate/envoyproxy_validate.go
index c5b83e57..70941f65 100644
--- a/extensions/envoyproxy_validate/envoyproxy_validate.go
+++ b/extensions/envoyproxy_validate/envoyproxy_validate.go
@@ -73,6 +73,7 @@ func flattenRules(prefix string, vv reflect.Value) (rules []ValidateRule) {
 		if vv.Len() == 0 {
 			return nil
 		}
+		fallthrough
 	default:
 		rules = append(rules, ValidateRule{Name: prefix, Value: vv.Interface()})
 	}
diff --git a/extensions/envoyproxy_validate/envoyproxy_validate_test.go b/extensions/envoyproxy_validate/envoyproxy_validate_test.go
index 3d5f3f10..7c6cae87 100644
--- a/extensions/envoyproxy_validate/envoyproxy_validate_test.go
+++ b/extensions/envoyproxy_validate/envoyproxy_validate_test.go
@@ -15,6 +15,7 @@ func TestTransform(t *testing.T) {
 		Type: &validate.FieldRules_String_{
 			String_: &validate.StringRules{
 				MinLen: proto.Uint64(1),
+				NotIn:  []string{"invalid"},
 			},
 		},
 	}
@@ -25,5 +26,6 @@ func TestTransform(t *testing.T) {
 	rules := transformed["validate.rules"].(ValidateExtension).Rules()
 	require.Equal(t, rules, []ValidateRule{
 		{Name: "string.min_len", Value: uint64(1)},
+		{Name: "string.not_in", Value: []string{"invalid"}},
 	})
 }