diff -u b/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
--- b/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -12,6 +12,7 @@
 use Drupal\Core\Config\ConfigNameException;
 use Drupal\Core\Config\Context\ContextInterface;
 use Drupal\Core\Config\TypedConfigManager;
+use Drupal\Core\TypedData\PrimitiveInterface;
 
 /**
  * Defines the default configuration object.
@@ -559,32 +560,21 @@
     }
     if (is_scalar($value)) {
       try {
-        $class = get_class($this->getSchemaForKey($key));
+        $element = $this->getSchemaForKey($key);
+        if ($element instanceof PrimitiveInterface) {
+          $value = $element->getCastedValue();
+        }
+        else {
+          // Config only supports primitive data types. If the config schema
+          // does define a type $element will be an instance of
+          // \Drupal\Core\Config\Schema\Property. Convert it to string since it
+          // is the safest possible type.
+          $value = $element->getString();
+        }
       }
       catch (\Exception $e) {
         // @todo throw an exception due to an incomplete schema. Only possible
         //   once https://drupal.org/node/1910624 is complete.
-        $class = FALSE;
-      }
-      switch ($class) {
-        case 'Drupal\Core\TypedData\Plugin\DataType\String':
-        case 'Drupal\Core\TypedData\Plugin\DataType\Uri':
-        case 'Drupal\Core\TypedData\Plugin\DataType\Email':
-        case 'Drupal\Core\Config\Schema\Property':
-          $value = (string) $value;
-          break;
-
-        case 'Drupal\Core\TypedData\Plugin\DataType\Integer':
-          $value = ($value !== '' ? (int) $value : NULL);
-          break;
-
-        case 'Drupal\Core\TypedData\Plugin\DataType\Boolean':
-          $value = ($value !== '' ? (bool) $value : NULL);
-          break;
-
-        case 'Drupal\Core\TypedData\Plugin\DataType\Float':
-          $value = ($value !== '' ? (float) $value : NULL);
-          break;
       }
     }
     else {
diff -u b/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTest.php b/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTest.php
--- b/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTest.php
+++ b/core/modules/config/lib/Drupal/config/Tests/ConfigSchemaTest.php
@@ -257,7 +257,7 @@
       'integer' => '100',
       'null_integer' => '',
       'boolean' => 1,
-      // In the config schema this doesn't have a type so should cast to string.
+      // If the config schema doesn't have a type it should be casted to string.
       'no_type' => 1,
       'array' => array(
         'string' => 1
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Binary.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Binary.php
@@ -89,4 +89,11 @@ public function getString() {
     }
     return $contents;
   }
+
+  /**
+   * @inheritdoc
+   */
+  public function getCastedValue() {
+    return $this->getValue();
+  }
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Boolean.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Boolean.php
@@ -25,4 +25,10 @@
  */
 class Boolean extends PrimitiveBase implements BooleanInterface {
 
+  /**
+   * @inheritdoc
+   */
+  public function getCastedValue() {
+    return ($this->value !== '' ? (bool) $this->value : NULL);
+  }
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Float.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Float.php
@@ -25,4 +25,10 @@
  */
 class Float extends PrimitiveBase implements FloatInterface {
 
+  /**
+   * @inheritdoc
+   */
+  public function getCastedValue() {
+    return ($this->value !== '' ? (float) $this->value : NULL);
+  }
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Integer.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Integer.php
@@ -25,4 +25,10 @@
  */
 class Integer extends PrimitiveBase implements IntegerInterface {
 
+  /**
+   * @inheritdoc
+   */
+  public function getCastedValue() {
+    return ($this->value !== '' ? (int) $this->value : NULL);
+  }
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/String.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/String.php
@@ -25,4 +25,10 @@
  */
 class String extends PrimitiveBase implements StringInterface {
 
+  /**
+   * @inheritdoc
+   */
+  public function getCastedValue() {
+    return (string) $this->value;
+  }
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Uri.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Uri.php
@@ -23,6 +23,6 @@
  *   label = @Translation("URI")
  * )
  */
-class Uri extends PrimitiveBase implements UriInterface {
+class Uri extends String implements UriInterface {
 
 }
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/TypedData/PrimitiveInterface.php
+++ b/core/lib/Drupal/Core/TypedData/PrimitiveInterface.php
@@ -28,4 +28,10 @@ public function getValue();
    */
   public function setValue($value);
 
+  /**
+   * Gets the primitive data value casted to the correct type.
+   *
+   * @return mixed
+   */
+  public function getCastedValue();
 }