diff --git a/core/lib/Drupal/Core/Plugin/Context/ContextHandler.php b/core/lib/Drupal/Core/Plugin/Context/ContextHandler.php
index c3f1fcd..efe7158 100644
--- a/core/lib/Drupal/Core/Plugin/Context/ContextHandler.php
+++ b/core/lib/Drupal/Core/Plugin/Context/ContextHandler.php
@@ -87,16 +87,17 @@ public function applyContextMapping(ContextAwarePluginInterface $plugin, $contex
         // Collect contexts that exist but are missing a value.
         if ($plugin_context_definition->isRequired() && !$contexts[$context_id]->hasContextValue()) {
           $missing_value[] = $plugin_context_id;
-          continue;
         }
-
-        if ($contexts[$context_id]->hasContextValue()) {
+        elseif ($contexts[$context_id]->hasContextValue()) {
           $plugin->setContextValue($plugin_context_id, $contexts[$context_id]->getContextValue());
         }
       }
       elseif ($plugin_context_definition->isRequired()) {
         $missing_value[] = $plugin_context_id;
-        continue;
+      }
+      else {
+        // Ignore mappings for optional missing context.
+        unset($mappings[$plugin_context_id]);
       }
     }
 
diff --git a/core/modules/system/tests/modules/condition_test/src/Plugin/Condition/OptionalContextCondition.php b/core/modules/system/tests/modules/condition_test/src/Plugin/Condition/OptionalContextCondition.php
new file mode 100644
index 0000000..986a66c
--- /dev/null
+++ b/core/modules/system/tests/modules/condition_test/src/Plugin/Condition/OptionalContextCondition.php
@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\condition_test\Plugin\Condition\OptionalContextCondition.
+ */
+
+namespace Drupal\condition_test\Plugin\Condition;
+
+use Drupal\Core\Condition\ConditionPluginBase;
+
+/**
+ * Provides a condition with optional context.
+ *
+ * @Condition(
+ *   id = "condition_test_optional_context",
+ *   label = @Translation("Optional context"),
+ *   context = {
+ *     "node" = @ContextDefinition("entity:node", label = @Translation("Node"), required = FALSE),
+ *   }
+ * )
+ */
+class OptionalContextCondition extends ConditionPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function evaluate() {
+    // Grant access if no context value is given.
+    return !$this->getContextValue('node');
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function summary() {
+    return $this->t('Context with optional context.');
+  }
+
+}
diff --git a/core/modules/system/tests/modules/condition_test/src/Tests/OptionalContextConditionTest.php b/core/modules/system/tests/modules/condition_test/src/Tests/OptionalContextConditionTest.php
new file mode 100644
index 0000000..f455905
--- /dev/null
+++ b/core/modules/system/tests/modules/condition_test/src/Tests/OptionalContextConditionTest.php
@@ -0,0 +1,74 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\condition_test\Tests\OptionalContextConditionTest.
+ */
+
+namespace Drupal\condition_test\Tests;
+
+use Drupal\Core\Plugin\Context\Context;
+use Drupal\Core\Plugin\Context\ContextDefinition;
+use Drupal\node\Entity\Node;
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests a condition with optional context.
+ *
+ * @group condition_test
+ */
+class OptionalContextConditionTest extends KernelTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['system', 'user', 'condition_test', 'node'];
+
+  /**
+   * Tests with both contexts mapped to the same user.
+   */
+  protected function testContextMissing() {
+    /** @var \Drupal\Core\Condition\ConditionPluginBase $condition */
+    $condition = \Drupal::service('plugin.manager.condition')
+      ->createInstance('condition_test_optional_context')
+      ->setContextMapping([
+        'node' => 'node',
+      ]);
+    \Drupal::service('context.handler')->applyContextMapping($condition, []);
+    $this->assertTrue($condition->execute());
+  }
+
+  /**
+   * Tests with both contexts mapped to the same user.
+   */
+  protected function testContextNoValue() {
+    /** @var \Drupal\Core\Condition\ConditionPluginBase $condition */
+    $condition = \Drupal::service('plugin.manager.condition')
+      ->createInstance('condition_test_optional_context')
+      ->setContextMapping([
+        'node' => 'node',
+      ]);
+    $definition = new ContextDefinition('entity:node');
+    $contexts['node'] = (new Context($definition));
+    \Drupal::service('context.handler')->applyContextMapping($condition, $contexts);
+    $this->assertTrue($condition->execute());
+  }
+
+  /**
+   * Tests with both contexts mapped to the same user.
+   */
+  protected function testContextAvailable() {
+    /** @var \Drupal\Core\Condition\ConditionPluginBase $condition */
+    $condition = \Drupal::service('plugin.manager.condition')
+      ->createInstance('condition_test_optional_context')
+      ->setContextMapping([
+        'node' => 'node',
+      ]);
+    $definition = new ContextDefinition('entity:node');
+    $node = Node::create(['type' => 'example']);
+    $contexts['node'] = (new Context($definition))->setContextValue($node);
+    \Drupal::service('context.handler')->applyContextMapping($condition, $contexts);
+    $this->assertFalse($condition->execute());
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Plugin/ContextHandlerTest.php b/core/tests/Drupal/Tests/Core/Plugin/ContextHandlerTest.php
index a852f33..f5345af 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/ContextHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/ContextHandlerTest.php
@@ -317,10 +317,10 @@ public function testApplyContextMappingMissingNotRequired() {
     $plugin = $this->getMock('Drupal\Tests\Core\Plugin\TestConfigurableContextAwarePluginInterface');
     $plugin->expects($this->once())
       ->method('getContextMapping')
-      ->willReturn([]);
+      ->willReturn(['optional' => 'missing']);
     $plugin->expects($this->once())
       ->method('getContextDefinitions')
-      ->will($this->returnValue(array('hit' => $context_definition)));
+      ->will($this->returnValue(array('optional' => $context_definition)));
     $plugin->expects($this->never())
       ->method('setContextValue');