diff --git a/types/types.go b/types/types.go
index d20ba6f..b79d2a2 100644
--- a/types/types.go
+++ b/types/types.go
@@ -514,7 +514,7 @@ func (d *Duration) Deref() time.Duration {
 func formatDuration(d time.Duration) string {
 	var sb strings.Builder
 	if d == 0 {
-		return "0"
+		return "0s"
 	}
 	if d < 0 {
 		sb.WriteByte('-')
diff --git a/types/types_test.go b/types/types_test.go
index a40d623..8516896 100644
--- a/types/types_test.go
+++ b/types/types_test.go
@@ -117,6 +117,7 @@ func TestFormatDuration(t *testing.T) {
 		d   time.Duration
 		str string
 	}{
+		{0, "0s"},
 		{5 * time.Second, "5s"},
 		{5 * time.Minute, "5m"},
 		{5 * time.Hour, "5h"},