diff --git a/api/prometheus/v1/api.go b/api/prometheus/v1/api.go
index 734a12e..2e506ae 100644
--- a/api/prometheus/v1/api.go
+++ b/api/prometheus/v1/api.go
@@ -138,7 +138,9 @@ func (h *httpAPI) Query(ctx context.Context, query string, ts time.Time) (model.
 	q := u.Query()
 
 	q.Set("query", query)
-	q.Set("time", ts.Format(time.RFC3339Nano))
+	if !ts.IsZero() {
+		q.Set("time", ts.Format(time.RFC3339Nano))
+	}
 
 	u.RawQuery = q.Encode()