diff --git a/htdocs/samples/chart_spline.html b/htdocs/samples/chart_spline.html
index ca1f5c8..0161b29 100644
--- a/htdocs/samples/chart_spline.html
+++ b/htdocs/samples/chart_spline.html
@@ -18,7 +18,12 @@
data1: 'spline',
data2: 'spline'
}
- }
+ },
+ spline: {
+ interpolation: {
+ type: 'monotone', // 'cardinal' is default
+ },
+ },
});