diff --git a/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
index eed4f89..f78d4d7 100644
--- a/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -581,6 +581,9 @@ protected function getSchemaWrapper() {
    *
    * @return mixed
    *   The value cast to the type indicated in the schema.
+   *
+   * @throws \Drupal\Core\Config\UnsupportedConfigDataTypeException
+   *   Exception on unsupported/undefined data type deducted.
    */
   protected function castValue($key, $value) {
     if ($value === NULL) {
@@ -616,9 +619,12 @@ protected function castValue($key, $value) {
       }
     }
     else {
-      // Any non-scalar value must be an array.
+      // Throw exception on any non-scalar or non-array value.
       if (!is_array($value)) {
-        $value = (array) $value;
+        throw new UnsupportedConfigDataTypeException(format_string('Invalid data type for config element @name:@key', array(
+          '@name' => $this->getName(),
+          '@key' => $key,
+        )));
       }
       // Recurse into any nested keys.
       foreach ($value as $nested_value_key => $nested_value) {
diff --git a/core/lib/Drupal/Core/Config/UnsupportedConfigDataTypeException.php b/core/lib/Drupal/Core/Config/UnsupportedConfigDataTypeException.php
new file mode 100644
index 0000000..ac63c26
--- /dev/null
+++ b/core/lib/Drupal/Core/Config/UnsupportedConfigDataTypeException.php
@@ -0,0 +1,14 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Config\UnsupportedConfigDataTypeException.
+ */
+
+namespace Drupal\Core\Config;
+
+/**
+ * Exception thrown when a config data type is invalid.
+ */
+class UnsupportedConfigDataTypeException extends ConfigException {
+}
diff --git a/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php
index 6d0714a..a46f1e5 100644
--- a/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigCRUDTest.php
@@ -10,6 +10,7 @@
 use Drupal\Core\Config\ConfigNameException;
 use Drupal\simpletest\DrupalUnitTestBase;
 use Drupal\Core\Config\FileStorage;
+use Drupal\Core\Config\UnsupportedConfigDataTypeException;
 
 /**
  * Tests CRUD operations on configuration objects.
@@ -229,7 +230,7 @@ public function testDataTypes() {
       $config->set('stream', fopen(__FILE__, 'r'))->save();
       $this->fail('No Exception thrown upon saving invalid data type.');
     }
-    catch (\Exception $e) {
+    catch (UnsupportedConfigDataTypeException $e) {
       $this->pass(format_string('%class thrown upon saving invalid data type.', array(
         '%class' => get_class($e),
       )));
diff --git a/core/modules/config/tests/config_test/config/schema/config_test.schema.yml b/core/modules/config/tests/config_test/config/schema/config_test.schema.yml
index 597e9f7..dbb4a37 100644
--- a/core/modules/config/tests/config_test/config/schema/config_test.schema.yml
+++ b/core/modules/config/tests/config_test/config/schema/config_test.schema.yml
@@ -131,3 +131,38 @@ config_test.schema_data_types:
       type: sequence
       sequence:
         - type: boolean
+
+config_test.types:
+  type: mapping
+  label: 'Configuration type'
+  mapping:
+    array:
+      type: sequence
+      label: 'Array'
+      sequence:
+        - type: string
+          label: 'Item'
+    boolean:
+      type: boolean
+      label: 'Boolean'
+    float:
+      type: float
+      label: 'Float'
+    exp:
+      type: float
+      label: 'Exponential'
+    hex:
+      type: integer
+      label: 'Hexadecimal'
+    int:
+      type: integer
+      label: 'Integer'
+    octal:
+      type: integer
+      label: 'Octal'
+    string:
+      type: string
+      label: 'String'
+    string_int:
+      type: string
+      label: 'String integer'