diff --git a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php
index 34eebe9..9bb1bfd 100644
--- a/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php
+++ b/core/lib/Drupal/Core/Field/Plugin/Field/FieldType/FloatItem.php
@@ -44,7 +44,10 @@ public static function schema(FieldStorageDefinitionInterface $field_definition)
     return array(
       'columns' => array(
         'value' => array(
+          // Use a big float so that MySQL, PostgreSQL and SQLite all use
+          // eight-byte floating-point numbers.
           'type' => 'float',
+          'size' => 'big',
         ),
       ),
     );
diff --git a/core/modules/field/src/Tests/Number/NumberFieldTest.php b/core/modules/field/src/Tests/Number/NumberFieldTest.php
index 0a22b74..b3bf19f 100644
--- a/core/modules/field/src/Tests/Number/NumberFieldTest.php
+++ b/core/modules/field/src/Tests/Number/NumberFieldTest.php
@@ -284,7 +284,12 @@ function testNumberFloatField() {
     preg_match('|entity_test/manage/(\d+)|', $this->url, $match);
     $id = $match[1];
     $this->assertText(t('entity_test @id has been created.', array('@id' => $id)), 'Entity was created');
-    $this->assertRaw(round($value, 2), 'Value is displayed.');
+    $this->assertRaw($value);
+
+    // Ensure that the 'number_decimal' formatter displays the number with the
+    // expected rounding.
+    $this->drupalGet('entity_test/' . $id);
+    $this->assertRaw(round($value, 2));
 
     // Try to create entries with more than one decimal separator; assert fail.
     $wrong_entries = array(