diff --git a/examples/custom-field/3-pair-field-json/index.ts b/examples/custom-field/3-pair-field-json/index.ts
index 5d39d824049..999b857b2fd 100644
--- a/examples/custom-field/3-pair-field-json/index.ts
+++ b/examples/custom-field/3-pair-field-json/index.ts
@@ -44,6 +44,7 @@ export function pair<ListTypeInfo extends BaseListTypeInfo>(
   config: PairFieldConfig<ListTypeInfo> = {}
 ): FieldTypeFunc<ListTypeInfo> {
   function resolveInput(value: PairInput | null | undefined) {
+    if (value === undefined) return undefined;
     const { left = null, right = null } = value ?? {};
     return JSON.stringify({ left, right });
   }
diff --git a/examples/custom-field/3-pair-field-nested/index.ts b/examples/custom-field/3-pair-field-nested/index.ts
index 3a30e635237..d1599e0feee 100644
--- a/examples/custom-field/3-pair-field-nested/index.ts
+++ b/examples/custom-field/3-pair-field-nested/index.ts
@@ -44,6 +44,7 @@ export function pair<ListTypeInfo extends BaseListTypeInfo>(
   config: PairFieldConfig<ListTypeInfo> = {}
 ): FieldTypeFunc<ListTypeInfo> {
   function resolveInput(value: PairInput | null | undefined) {
+    if (value === undefined) return undefined;
     const { left = null, right = null } = value ?? {};
     return { left, right };
   }
diff --git a/examples/custom-field/3-pair-field/index.ts b/examples/custom-field/3-pair-field/index.ts
index 4e105ec7184..8eb8d463492 100644
--- a/examples/custom-field/3-pair-field/index.ts
+++ b/examples/custom-field/3-pair-field/index.ts
@@ -26,7 +26,7 @@ export function pair<ListTypeInfo extends BaseListTypeInfo>(
   config: PairFieldConfig<ListTypeInfo> = {}
 ): FieldTypeFunc<ListTypeInfo> {
   function resolveInput(value: PairInput | null | undefined) {
-    if (!value) return { left: value, right: value };
+    if (value === undefined) return undefined;
     const [left = '', right = ''] = value.split(' ', 2);
     return {
       left,