diff --git a/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
index c0d2617..6c4c3b7 100644
--- a/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -189,13 +189,6 @@ public function isNew() {
    *   would return array('bar' => 'baz').
    *   If no key is specified, then the entire data array is returned.
    *
-   * The configuration system does not retain data types. Every saved value is
-   * casted to a string. In most cases this is not an issue; however, it can
-   * cause issues with Booleans, which are casted to "1" (TRUE) or "0" (FALSE).
-   * In particular, code relying on === or !== will no longer function properly.
-   *
-   * @see http://php.net/manual/language.operators.comparison.php
-   *
    * @return mixed
    *   The data that was requested.
    */
@@ -319,8 +312,6 @@ public function set($key, $value) {
     if (!$this->isLoaded) {
       $this->load();
     }
-    // Type-cast value into a string.
-    $value = $this->castValue($value);
 
     // The dot/period is a reserved character; it may appear between keys, but
     // not within keys.
@@ -336,46 +327,6 @@ public function set($key, $value) {
   }
 
   /**
-   * Casts a saved value to a string.
-   *
-   * The configuration system only saves strings or arrays. Any scalar
-   * non-string value is cast to a string. The one exception is boolean FALSE
-   * which would normally become '' when cast to a string, but is manually
-   * cast to '0' here for convenience and consistency.
-   *
-   * Any non-scalar value that is not an array (aka objects) gets cast
-   * to an array.
-   *
-   * @param mixed $value
-   *   A value being saved into the configuration system.
-   *
-   * @return string
-   *   The value cast to a string or array.
-   */
-  public function castValue($value) {
-    if (is_scalar($value) || $value === NULL) {
-      // Handle special case of FALSE, which should be '0' instead of ''.
-      if ($value === FALSE) {
-        $value = '0';
-      }
-      else {
-        $value = (string) $value;
-      }
-    }
-    else {
-      // Any non-scalar value must be an array.
-      if (!is_array($value)) {
-        $value = (array) $value;
-      }
-      // Recurse into any nested keys.
-      foreach ($value as $key => $nested_value) {
-        $value[$key] = $this->castValue($nested_value);
-      }
-    }
-    return $value;
-  }
-
-  /**
    * Unsets value in this config object.
    *
    * @param string $key
diff --git a/core/lib/Drupal/Core/Config/FileStorage.php b/core/lib/Drupal/Core/Config/FileStorage.php
index 6422e9d..a08af4b 100644
--- a/core/lib/Drupal/Core/Config/FileStorage.php
+++ b/core/lib/Drupal/Core/Config/FileStorage.php
@@ -140,6 +140,7 @@ protected function getDumper() {
       // 2 spaces for consistency with Drupal coding standards.
       $this->dumper->setIndentation(2);
     }
+
     return $this->dumper;
   }
 
@@ -162,8 +163,9 @@ protected function getParser() {
    */
   public function encode($data) {
     // The level where you switch to inline YAML is set to PHP_INT_MAX to ensure
-    // this does not occur.
-    return $this->getDumper()->dump($data, PHP_INT_MAX);
+    // this does not occur. Also set the exceptionOnInvalidType parameter to
+    // TRUE, so exceptions are thrown for an invalid data type.
+    return $this->getDumper()->dump($data, PHP_INT_MAX, 0, TRUE);
   }
 
   /**
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php
index ec4e7cd..7dcd1b4 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockStorageUnitTest.php
@@ -92,15 +92,15 @@ protected function createTests() {
     // Ensure that default values are filled in.
     $expected_properties = array(
       'id' => 'stark.test_block',
-      'label' => '',
-      'region' => '-1',
-      'weight' => '',
+      'label' => NULL,
+      'region' => -1,
+      'weight' => NULL,
       'module' => 'block_test',
-      'status' => '1',
+      'status' => TRUE,
       'visibility' => array(),
       'plugin' => 'test_html_id',
       'settings' => array(
-        'cache' => '1',
+        'cache' => 1,
         'admin_label' => t('Test block html id'),
       ),
       'langcode' => LANGUAGE_NOT_SPECIFIED,
diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php
index bb17201..ff67cf7 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Tests/CKEditorAdminTest.php
@@ -160,10 +160,10 @@ function testAdmin() {
     $this->drupalGet('admin/config/content/formats/filtered_html');
     $ultra_llama_mode_checkbox = $this->xpath('//input[@type="checkbox" and @name="editor[settings][plugins][llama_contextual_and_button][ultra_llama_mode]" and @checked="checked"]');
     $this->assertTrue(count($ultra_llama_mode_checkbox) === 1, 'The "Ultra llama mode" checkbox exists and is checked.');
-    $expected_settings['plugins']['llama_contextual_and_button']['ultra_llama_mode'] = '1';
+    $expected_settings['plugins']['llama_contextual_and_button']['ultra_llama_mode'] = 1;
     $editor = entity_load('editor', 'filtered_html');
     $this->assertTrue($editor instanceof Editor, 'An Editor config entity exists.');
-    $this->assertIdentical($expected_settings, $editor->settings, 'The Editor config entity has the correct settings.');
+    $this->assertIdentical($expected_settings, $editor->settings);
   }
 
 }
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php
index b6bded3..fec4aee 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php
@@ -9,6 +9,7 @@
 
 use Drupal\Core\Config\ConfigNameException;
 use Drupal\simpletest\DrupalUnitTestBase;
+use Drupal\Core\Config\FileStorage;
 
 /**
  * Tests CRUD operations on configuration objects.
@@ -181,4 +182,53 @@ function testNameValidation() {
     $this->assertFalse(config_import(), "Config import failed when trying to importing an object with an invalid name");
   }
 
+  /**
+   * Tests data type handling.
+   */
+  function testDataTypes() {
+    module_enable(array('config_test'));
+    $storage = new FileStorage($this->configDirectories[CONFIG_ACTIVE_DIRECTORY]);
+    $name = 'config_test.types';
+    $config = config($name);
+
+    $original_content = file_get_contents($storage->getFilePath($name));
+    $this->verbose('<pre>' . $original_content . "\n" . var_export($storage->read($name), TRUE));
+
+    // Verify variable data types are intact.
+    $data = array(
+      'array' => array(),
+      'boolean' => TRUE,
+      'exp' => 1.2e+34,
+      'float' => 3.14159,
+      'hex' => 0xC,
+      'int' => 99,
+      'octal' => 0775,
+      'string' => 'string',
+      'string_int' => '1',
+    );
+    $this->assertIdentical($config->get(), $data);
+
+    // Re-set each key using Config::set().
+    foreach($data as $key => $value) {
+      $config->set($key, $value);
+    }
+    $config->save();
+    $this->assertIdentical($config->get(), $data);
+    $this->verbose('<pre>' . file_get_contents($storage->getFilePath($name)) . var_export($storage->read($name), TRUE));
+
+    // Set data using config::setData().
+    $config->setData($data)->save();
+    $this->assertIdentical($config->get(), $data);
+
+    try {
+      $config->set('stream', fopen(__FILE__, 'r'))->save();
+      $this->fail('No Exception thrown upon saving invalid data type.');
+    }
+    catch (\Exception $e) {
+      $this->pass(format_string('%class thrown upon saving invalid data type.', array(
+        '%class' => get_class($e),
+      )));
+    }
+  }
+
 }
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php
index e93b79f..dff3293 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigEntityTest.php
@@ -148,8 +148,7 @@ function testCRUD() {
     // Verify that the entity was overwritten.
     $same_id = entity_load('config_test', $config_test->id());
     $this->assertIdentical($same_id->id(), $config_test->id());
-    // Note: Reloading loads from FileStorage, and FileStorage enforces strings.
-    $this->assertIdentical($same_id->label(), '');
+    $this->assertIdentical($same_id->label(), NULL);
     $this->assertNotEqual($same_id->uuid(), $config_test->uuid());
 
     // Revert to previous state.
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigFileContentTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigFileContentTest.php
index f2e7965..7d4e43a 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigFileContentTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigFileContentTest.php
@@ -123,7 +123,7 @@ function testReadWriteConfig() {
     $this->assertEqual($config->get($true_key), '1', format_string("Boolean TRUE value returned the string '1'."));
 
     // Read null value.
-    $this->assertIdentical($config->get('null'), '');
+    $this->assertIdentical($config->get('null'), NULL);
 
     // Read false that had been nested in an array value
     $this->assertEqual($config->get($casting_array_false_value_key), '0', format_string("Nested boolean FALSE value returned the string '0'."));
diff --git a/core/modules/config/lib/Drupal/config/Tests/Storage/ConfigStorageTestBase.php b/core/modules/config/lib/Drupal/config/Tests/Storage/ConfigStorageTestBase.php
index a2b3448..8b3fc54 100644
--- a/core/modules/config/lib/Drupal/config/Tests/Storage/ConfigStorageTestBase.php
+++ b/core/modules/config/lib/Drupal/config/Tests/Storage/ConfigStorageTestBase.php
@@ -161,6 +161,30 @@ function testCRUD() {
 
   }
 
+  /**
+   * Tests storage controller writing and reading data preserving data type.
+   */
+  function testDataTypes() {
+    $name = 'config_test.types';
+    $data = array(
+      'array' => array(),
+      'boolean' => TRUE,
+      'exp' => 1.2e+34,
+      'float' => 3.14159,
+      'hex' => 0xC,
+      'int' => 99,
+      'octal' => 0775,
+      'string' => 'string',
+    );
+
+    $result = $this->storage->write($name, $data);
+    $this->assertIdentical($result, TRUE);
+
+    $read_data = $this->storage->read($name);
+    $this->assertIdentical($read_data, $data);
+  }
+
+
   abstract protected function read($name);
 
   abstract protected function insert($name, $data);
diff --git a/core/modules/config/tests/config_test/config/config_test.types.yml b/core/modules/config/tests/config_test/config/config_test.types.yml
new file mode 100644
index 0000000..4ab2cdc
--- /dev/null
+++ b/core/modules/config/tests/config_test/config/config_test.types.yml
@@ -0,0 +1,9 @@
+array: []
+boolean: true
+exp: 1.2e+34
+float: 3.14159
+hex: 0xC
+int: 99
+octal: 0775
+string: string
+string_int: '1'
diff --git a/core/modules/system/lib/Drupal/system/Tests/Module/ModuleEnable.php b/core/modules/system/lib/Drupal/system/Tests/Module/ModuleEnable.php
index b2d08fc..517a544 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Module/ModuleEnable.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Module/ModuleEnable.php
@@ -31,7 +31,7 @@ public static function getInfo() {
    */
   function testEnableUserTwice() {
     module_enable(array('user'), FALSE);
-    $this->assertIdentical(config('system.module')->get('enabled.user'), '0');
+    $this->assertIdentical(config('system.module')->get('enabled.user'), 0);
   }
 
   /**