diff --git a/core/modules/telephone/config/schema/telephone.schema.yml b/core/modules/telephone/config/schema/telephone.schema.yml
index dc8713a341bfa96bc0a869162910cfb9bec006db..516cbc3459dd4c02d0ec6d6c706e562eb9da2896 100644
--- a/core/modules/telephone/config/schema/telephone.schema.yml
+++ b/core/modules/telephone/config/schema/telephone.schema.yml
@@ -15,3 +15,11 @@ field.widget.settings.telephone_default:
     placeholder:
       type: label
       label: 'Placeholder'
+
+field.value.telephone:
+  type: mapping
+  label: 'Default value'
+  mapping:
+    value:
+      type: string
+      label: 'Value'
diff --git a/core/modules/telephone/tests/src/Kernel/TelephoneItemTest.php b/core/modules/telephone/tests/src/Kernel/TelephoneItemTest.php
index 72269409e4387b6e6c6e08ef964cac5c7d2193f8..6e635acc7d80204cef338a6e048bd5982b32b019 100644
--- a/core/modules/telephone/tests/src/Kernel/TelephoneItemTest.php
+++ b/core/modules/telephone/tests/src/Kernel/TelephoneItemTest.php
@@ -36,6 +36,7 @@ protected function setUp() {
       'entity_type' => 'entity_test',
       'field_name' => 'field_test',
       'bundle' => 'entity_test',
+      'default_value' => [0 => ['value' => '+012345678']],
     ])->save();
   }