diff --git a/core/lib/Drupal/Core/Config/Schema/Mapping.php b/core/lib/Drupal/Core/Config/Schema/Mapping.php
index 0a975cf..a85fac4 100644
--- a/core/lib/Drupal/Core/Config/Schema/Mapping.php
+++ b/core/lib/Drupal/Core/Config/Schema/Mapping.php
@@ -50,7 +50,7 @@ public function get($property_name) {
     if (isset($elements[$root_key])) {
       $element = $elements[$root_key];
       // If $property_name contained a dot recurse into the keys.
-      while ($element && $key = array_shift($parts)) {
+      while ($element && ($key = array_shift($parts)) !== NULL) {
         if (method_exists($element, 'get')) {
           $element = $element->get($key);
         }
@@ -130,7 +130,7 @@ public function getPropertyDefinitions() {
     if (!isset($this->propertyDefinitions)) {
       $this->propertyDefinitions = array();
       foreach ($this->getAllKeys() as $key) {
-        $definition = isset($this->definition['mapping'][$name]) ? $this->definition['mapping'][$name] : array();
+        $definition = isset($this->definition['mapping'][$key]) ? $this->definition['mapping'][$key] : array();
         $this->propertyDefinitions[$key] = $this->buildDataDefinition($definition, $this->value[$key], $key);
       }
     }
diff --git a/core/modules/config/src/Tests/SchemaCheckTraitTest.php b/core/modules/config/src/Tests/SchemaCheckTraitTest.php
index 3b5793a..5620422 100644
--- a/core/modules/config/src/Tests/SchemaCheckTraitTest.php
+++ b/core/modules/config/src/Tests/SchemaCheckTraitTest.php
@@ -64,12 +64,15 @@ public function testTrait() {
     $ret = $this->checkConfigSchema($this->typedConfig, 'config_test.types', $config_data);
     $this->assertIdentical($ret, TRUE);
 
-    // Add a new key and new array to test the error messages.
+    // Add a new key, a new array and overwrite boolean with array to test the
+    // error messages.
     $config_data = array('new_key' => 'new_value', 'new_array' => array()) + $config_data;
+    $config_data['boolean'] = array();
     $ret = $this->checkConfigSchema($this->typedConfig, 'config_test.types', $config_data);
     $expected = array(
-      'config_test.types:new_key' => 'Missing schema',
-      'config_test.types:new_array' => 'Non-scalar value but not defined as an array (such as mapping or sequence)',
+      'config_test.types:new_key' => 'Missing schema.',
+      'config_test.types:new_array' => 'Missing schema.',
+      'config_test.types:boolean' => 'Non-scalar value but not defined as an array (such as mapping or sequence).',
     );
     $this->assertIdentical($ret, $expected);
   }