diff --git a/go/jsruntime/uikit/Chart.tsx b/go/jsruntime/uikit/Chart.tsx
index 90bec626..c6c12d8d 100644
--- a/go/jsruntime/uikit/Chart.tsx
+++ b/go/jsruntime/uikit/Chart.tsx
@@ -885,8 +885,7 @@ function Legend(p: { props: ChartProps; legend: ChartLegend | null; colorOf: (i:
     // row under the plot. An explicit ChartLegend picks the row/column axis (orientation)
     // and where along it the legend sits (position).
     const containerClass = () => {
-        const cfg = p.legend;
-        if (!cfg) return "mt-3 flex flex-wrap items-center gap-x-4 gap-y-1.5";
+        const cfg = p.legend ?? {orientation: "horizontal", position: "bottom-center"};
         if (cfg.orientation === "vertical") {
             const justify = cfg.position.startsWith("top") ? "justify-start"
                 : cfg.position.startsWith("bottom") ? "justify-end" : "justify-center";