diff --git a/src/plugins/pricelist/components/CalculationTable/DrinkPriceVolumes.vue b/src/plugins/pricelist/components/CalculationTable/DrinkPriceVolumes.vue
index a0ee546..be0142e 100644
--- a/src/plugins/pricelist/components/CalculationTable/DrinkPriceVolumes.vue
+++ b/src/plugins/pricelist/components/CalculationTable/DrinkPriceVolumes.vue
@@ -68,8 +68,8 @@ export default defineComponent({
     },
   },
   setup(props) {
-    const _volume = ref<number>();
-    const volume = computed({
+    const _volume = ref<number|undefined>();
+    const volume = computed<number|undefined>({
       get: () => {
         if (_volume.value !== undefined) {
           return _volume.value;
@@ -77,9 +77,9 @@ export default defineComponent({
         if (props.props.volumes.length > 0) {
           return props.props.volumes[0].id;
         }
-        return null;
+        return undefined;
       },
-      set: (val: number) => (_volume.value = val),
+      set: (val: number|undefined) => (_volume.value = val),
     });
     return { volume };
   },