diff --git a/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php b/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
index 6d6e6edc1f3..08a53c09af6 100644
--- a/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
+++ b/core/lib/Drupal/Core/Database/Driver/sqlite/Schema.php
@@ -505,11 +505,9 @@ protected function introspectSchema($table) {
           'type' => $type,
           'size' => $size,
           'not null' => !empty($row->notnull) || $row->pk !== "0",
-          // @todo decide whether this more correct change is better than ?? ''.
-          //   The problem with the current code is that an empty string as a
-          //   default value is not the same as a NULL but we current make it
-          //   the same thing.
-          'default' => $row->dflt_value !== NULL ? trim($row->dflt_value, "'") : NULL,
+          // Only trim string values. Other values such as NULLs should be
+          // preserved.
+          'default' => is_string($row->dflt_value) ? trim($row->dflt_value, "'") : $row->dflt_value,
         ];
         if ($length) {
           $schema['fields'][$row->name]['length'] = $length;
diff --git a/core/tests/Drupal/KernelTests/Core/Database/SchemaTest.php b/core/tests/Drupal/KernelTests/Core/Database/SchemaTest.php
index eb8ea41d376..cfe6386d0b4 100644
--- a/core/tests/Drupal/KernelTests/Core/Database/SchemaTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Database/SchemaTest.php
@@ -1276,4 +1276,39 @@ public function testUpperCaseTableName() {
     $this->assertTrue($this->schema->dropTable($table_name), 'Table with uppercase table name dropped');
   }
 
+  /**
+   * Tests NULL default value after altering table.
+   */
+  public function testNullDefaultAfterAlter() {
+    $table_name = 'test_table';
+
+    // Create the tables.
+    $table_specification = [
+      'description' => 'Test table.',
+      'fields' => [
+        'column1'  => [
+          'type' => 'int',
+          'default' => NULL,
+        ],
+        'column2'  => [
+          'type' => 'varchar',
+          'length' => 20,
+          'default' => NULL,
+        ],
+      ],
+    ];
+    $this->schema->createTable($table_name, $table_specification);
+
+    // Insert a column and check that column 2 has the expected default value.
+    $this->connection->insert($table_name)->fields(['column1' => 1])->execute();
+    $this->assertNull($this->connection->select($table_name, 't')->fields('t', ['column2'])->condition('column1', 1)->execute()->fetchField());
+
+    // Force SQLite schema to create a new table and copy data.
+    $this->schema->addField('test_table', 'column3', ['type' => 'varchar', 'length' => 20, 'not null' => TRUE, 'description' => 'Added column 3.', 'initial' => 'test']);
+
+    // Test that the column 2 default NULL value still works.
+    $this->connection->insert($table_name)->fields(['column1' => 2, 'column3' => 'value'])->execute();
+    $this->assertNull($this->connection->select($table_name, 't')->fields('t', ['column2'])->condition('column1', 2)->execute()->fetchField());
+  }
+
 }