diff --git a/src/plugins/vis_types/xy/public/config/get_config.ts b/src/plugins/vis_types/xy/public/config/get_config.ts
index d7cf22625e10e..7aad30c5b743e 100644
--- a/src/plugins/vis_types/xy/public/config/get_config.ts
+++ b/src/plugins/vis_types/xy/public/config/get_config.ts
@@ -6,7 +6,7 @@
  * Side Public License, v 1.
  */
 
-import { ScaleContinuousType } from '@elastic/charts';
+import { Fit, ScaleContinuousType } from '@elastic/charts';
 
 import { Datatable } from '../../../../expressions/public';
 import { BUCKET_TYPES } from '../../../../data/public';
@@ -92,7 +92,7 @@ export function getConfig(
   return {
     // NOTE: downscale ratio to match current vislib implementation
     markSizeRatio: radiusRatio * 0.6,
-    fittingFunction,
+    fittingFunction: fittingFunction ?? Fit.Linear,
     fillOpacity,
     detailedTooltip,
     orderBucketsBySum,
diff --git a/src/plugins/vis_types/xy/public/editor/components/options/point_series/elastic_charts_options.tsx b/src/plugins/vis_types/xy/public/editor/components/options/point_series/elastic_charts_options.tsx
index 105cd66799041..1c93fe92b79af 100644
--- a/src/plugins/vis_types/xy/public/editor/components/options/point_series/elastic_charts_options.tsx
+++ b/src/plugins/vis_types/xy/public/editor/components/options/point_series/elastic_charts_options.tsx
@@ -78,7 +78,7 @@ export function ElasticChartsOptions(props: ValidationVisOptionsProps<VisParams>
           })}
           options={fittingFunctions}
           paramName="fittingFunction"
-          value={stateParams.fittingFunction}
+          value={stateParams.fittingFunction ?? fittingFunctions[2].value}
           setValue={(paramName, value) => {
             if (trackUiMetric) {
               trackUiMetric(METRIC_TYPE.CLICK, 'fitting_function_selected');