diff --git a/client/components/planning-editor-standalone/field-adapters/custom-vocabularies.ts b/client/components/planning-editor-standalone/field-adapters/custom-vocabularies.ts
index 1bb5da8af..053b94189 100644
--- a/client/components/planning-editor-standalone/field-adapters/custom-vocabularies.ts
+++ b/client/components/planning-editor-standalone/field-adapters/custom-vocabularies.ts
@@ -47,7 +47,7 @@ export const getCustomVocabularyFields = () => {
                         }));
 
                         // Remove values that don't match the "subfield" ID, so there's no item duplication
-                        const restOfValues = item.subject.filter((x) => x.scheme !== id);
+                        const restOfValues = (item.subject ?? []).filter((x) => x.scheme !== id);
 
                         return {
                             ...item,
diff --git a/client/components/planning-editor-standalone/profile-converter.ts b/client/components/planning-editor-standalone/profile-converter.ts
index 0484760d1..36c6ebba0 100644
--- a/client/components/planning-editor-standalone/profile-converter.ts
+++ b/client/components/planning-editor-standalone/profile-converter.ts
@@ -17,7 +17,7 @@ type IFieldConverted = IBaseField<'normal'> | ICustomVocabularyField;
 export const getProfileFieldsConverted = (): Array<IFieldConverted> => {
     const planningProfile = planningApi.contentProfiles.get('planning');
     const planningGroups = getEditorFormGroupsFromProfile(planningProfile);
-    const planningFieldIds = flatMap(Object.values(planningGroups).map((x) => x.fields));
+    const planningFieldIds = Object.values(planningGroups).flatMap((x) => x.fields);
     const convertedFieldIds: Array<IFieldConverted> = [];
 
     for (const fieldId of planningFieldIds) {