diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index 79e3f14..3d4f3a0 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -491,7 +491,7 @@ field.value.string_long:
 # Schema for the configuration of the URI field type.
 
 field.storage_settings.uri:
-  type: mapping
+  type: field.storage_settings.string
   label: 'URI settings'
   mapping:
     max_length:
diff --git a/core/config/schema/core.entity.schema.yml b/core/config/schema/core.entity.schema.yml
index cc1a57e..71b7ccd 100644
--- a/core/config/schema/core.entity.schema.yml
+++ b/core/config/schema/core.entity.schema.yml
@@ -160,6 +160,17 @@ field.widget.settings.string_textarea:
       type: label
       label: 'Placeholder'
 
+field.widget.settings.uri:
+  type: mapping
+  label: 'URI field'
+  mapping:
+    size:
+      type: integer
+      label: 'Size of URI field'
+    placeholder:
+      type: label
+      label: 'Placeholder'
+
 field.widget.settings.email_default:
   type: mapping
   label: 'Email field display format settings'
diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
index 3f7805b..1481d88 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/UriItem.php
@@ -32,9 +32,11 @@ class UriItem extends StringItem {
    * {@inheritdoc}
    */
   public static function defaultStorageSettings() {
-    return array(
-      'max_length' => 2048,
-    ) + parent::defaultStorageSettings();
+    $storage_settings = parent::defaultStorageSettings();
+    // is_ascii doesn't make sense for URIs.
+    unset($storage_settings['is_ascii']);
+    $storage_settings['max_length'] = 2048;
+    return $storage_settings;
   }
 
   /**
diff --git a/core/modules/field/src/Tests/Uri/UriItemTest.php b/core/modules/field/src/Tests/Uri/UriItemTest.php
new file mode 100644
index 0000000..46ffe0a
--- /dev/null
+++ b/core/modules/field/src/Tests/Uri/UriItemTest.php
@@ -0,0 +1,73 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\field\Tests\Uri\UriItemTest.
+ */
+
+namespace Drupal\field\Tests\Uri;
+
+use Drupal\Component\Utility\Unicode;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\field\Tests\FieldUnitTestBase;
+
+/**
+ * Tests URI field functionality.
+ *
+ * @see \Drupal\Core\Field\Plugin\Field\FieldType\UriItem
+ *
+ * @group field
+ */
+class UriItemTest extends FieldUnitTestBase {
+
+  /**
+   * A field to use in this test class.
+   *
+   * @var \Drupal\field\Entity\FieldStorageConfig
+   */
+  protected $fieldStorage;
+
+  /**
+   * The field used in this test class.
+   *
+   * @var \Drupal\field\Entity\FieldConfig
+   */
+  protected $field;
+
+  /**
+   * Tests URI field.
+   */
+  public function testUriField() {
+    $label = $this->randomMachineName();
+
+    // Create a field with settings to validate.
+    $field_name = Unicode::strtolower($this->randomMachineName());
+    $this->fieldStorage = FieldStorageConfig::create([
+      'field_name' => $field_name,
+      'entity_type' => 'entity_test',
+      'type' => 'uri',
+    ]);
+    $this->fieldStorage->save();
+    $this->field = FieldConfig::create([
+      'field_name' => $field_name,
+      'entity_type' => 'entity_test',
+      'bundle' => 'entity_test',
+      'label' => $label,
+      'required' => TRUE,
+      'settings' => [
+        'size' => 123,
+        'placeholder' => '',
+      ],
+    ]);
+    $this->field->save();
+
+    // Create a form display for the default form mode.
+    entity_get_form_display('entity_test', 'entity_test', 'default')
+      ->setComponent($field_name, [
+        'type' => 'uri',
+      ])
+      ->save();
+  }
+
+}