diff --git a/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php b/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php
index 2ba0a7e..ba8029d 100644
--- a/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php
+++ b/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php
@@ -130,9 +130,9 @@ public function validateContexts();
    *
    * @return array
    *   A mapping of the expected assignment names to their context names. For
-   *   example, if one of the $contexts is named 'current_user', but the plugin
+   *   example, if one of the $contexts is named 'user.current_user', but the plugin
    *   expects a context named 'user', then this map would contain
-   *   'current_user' => 'user'.
+   *   'user' => 'user.current_user'.
    */
   public function getContextMapping();
 
@@ -141,9 +141,9 @@ public function getContextMapping();
    *
    * @param array $context_mapping
    *   A mapping of the expected assignment names to their context names. For
-   *   example, if one of the $contexts is named 'current_user', but the plugin
+   *   example, if one of the $contexts is named 'user.current_user', but the plugin
    *   expects a context named 'user', then this map would contain
-   *   'current_user' => 'user'.
+   *   'user' => 'user.current_user'.
    *
    * @return $this
    */
diff --git a/core/lib/Drupal/Core/Plugin/Context/ContextHandler.php b/core/lib/Drupal/Core/Plugin/Context/ContextHandler.php
index 019ad4e..4888ee3 100644
--- a/core/lib/Drupal/Core/Plugin/Context/ContextHandler.php
+++ b/core/lib/Drupal/Core/Plugin/Context/ContextHandler.php
@@ -73,22 +73,20 @@ public function getMatchingContexts(array $contexts, ContextDefinitionInterface
    */
   public function applyContextMapping(ContextAwarePluginInterface $plugin, $contexts, $mappings = array()) {
     $mappings += $plugin->getContextMapping();
-    $plugin_contexts = $plugin->getContextDefinitions();
-    // Loop through each context and set it on the plugin if it matches one of
-    // the contexts expected by the plugin.
-    foreach ($contexts as $name => $context) {
+    // Loop through each of the expected contexts.
+    foreach (array_keys($plugin->getContextDefinitions()) as $plugin_context_id) {
       // If this context was given a specific name, use that.
-      $assigned_name = isset($mappings[$name]) ? $mappings[$name] : $name;
-      if (isset($plugin_contexts[$assigned_name])) {
+      $context_id = isset($mappings[$plugin_context_id]) ? $mappings[$plugin_context_id] : $plugin_context_id;
+      if (!empty($contexts[$context_id])) {
         // This assignment has been used, remove it.
-        unset($mappings[$name]);
-        $plugin->setContextValue($assigned_name, $context->getContextValue());
+        unset($mappings[$plugin_context_id]);
+        $plugin->setContextValue($plugin_context_id, $contexts[$context_id]->getContextValue());
       }
     }
 
     // If there are any mappings that were not satisfied, throw an exception.
     if (!empty($mappings)) {
-      throw new ContextException(String::format('Assigned contexts were not satisfied: @mappings', array('@mappings' => implode(',', $mappings))));
+      throw new ContextException(String::format('Assigned contexts were not satisfied: @mappings', ['@mappings' => implode(',', array_keys($mappings))]));
     }
   }
 
diff --git a/core/lib/Drupal/Core/Plugin/Context/ContextHandlerInterface.php b/core/lib/Drupal/Core/Plugin/Context/ContextHandlerInterface.php
index bd0ade5..b14b594 100644
--- a/core/lib/Drupal/Core/Plugin/Context/ContextHandlerInterface.php
+++ b/core/lib/Drupal/Core/Plugin/Context/ContextHandlerInterface.php
@@ -70,9 +70,9 @@ public function getMatchingContexts(array $contexts, ContextDefinitionInterface
    *   match the plugin's context definitions.
    * @param array $mappings
    *   (optional) A mapping of the expected assignment names to their context
-   *   names. For example, if one of the $contexts is named 'entity', but the
-   *   plugin expects a context named 'node', then this map would contain
-   *   'entity' => 'node'.
+   *   names. For example, if one of the $contexts is named 'current_user', but the
+   *   plugin expects a context named 'user', then this map would contain
+   *   'user' => 'current_user'.
    *
    * @throws \Drupal\Component\Plugin\Exception\ContextException
    *   Thrown when a context assignment was not satisfied.
diff --git a/core/lib/Drupal/Core/Plugin/ContextAwarePluginBase.php b/core/lib/Drupal/Core/Plugin/ContextAwarePluginBase.php
index 3cfa678..5329d56 100644
--- a/core/lib/Drupal/Core/Plugin/ContextAwarePluginBase.php
+++ b/core/lib/Drupal/Core/Plugin/ContextAwarePluginBase.php
@@ -55,7 +55,7 @@ public function setContext($name, ComponentContextInterface $context) {
    */
   public function getContextMapping() {
     $configuration = $this instanceof ConfigurablePluginInterface ? $this->getConfiguration() : $this->configuration;
-    return isset($configuration['context_mapping']) ? array_flip($configuration['context_mapping']) : [];
+    return isset($configuration['context_mapping']) ? $configuration['context_mapping'] : [];
   }
 
   /**
diff --git a/core/modules/system/tests/modules/condition_test/src/Plugin/Condition/ConditionTestDualUser.php b/core/modules/system/tests/modules/condition_test/src/Plugin/Condition/ConditionTestDualUser.php
new file mode 100644
index 0000000..0311b0e
--- /dev/null
+++ b/core/modules/system/tests/modules/condition_test/src/Plugin/Condition/ConditionTestDualUser.php
@@ -0,0 +1,42 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\condition_test\Plugin\Condition\ConditionTestDualUser.
+ */
+
+namespace Drupal\condition_test\Plugin\Condition;
+
+use Drupal\Core\Condition\ConditionPluginBase;
+
+/**
+ * Provides a condition that requires two users.
+ *
+ * @Condition(
+ *   id = "condition_test_dual_user",
+ *   label = @Translation("Dual user"),
+ *   context = {
+ *     "user1" = @ContextDefinition("entity:user", label = @Translation("User 1")),
+ *     "user2" = @ContextDefinition("entity:user", label = @Translation("User 2"))
+ *   }
+ * )
+ */
+class ConditionTestDualUser extends ConditionPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function evaluate() {
+    $user1 = $this->getContextValue('user1');
+    $user2 = $this->getContextValue('user2');
+    return $user1->id() === $user2->id();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function summary() {
+    return $this->t('This condition has two users.');
+  }
+
+}
diff --git a/core/modules/system/tests/modules/condition_test/src/Tests/ConditionTestDualUserTest.php b/core/modules/system/tests/modules/condition_test/src/Tests/ConditionTestDualUserTest.php
new file mode 100644
index 0000000..ab498ba
--- /dev/null
+++ b/core/modules/system/tests/modules/condition_test/src/Tests/ConditionTestDualUserTest.php
@@ -0,0 +1,98 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\condition_test\Tests\ConditionTestDualUserTest.
+ */
+
+namespace Drupal\condition_test\Tests;
+
+use Drupal\Core\Plugin\Context\Context;
+use Drupal\Core\Plugin\Context\ContextDefinition;
+use Drupal\simpletest\KernelTestBase;
+use Drupal\user\Entity\User;
+
+/**
+ * Tests a condition that requires two users.
+ *
+ * @group condition_test
+ */
+class ConditionTestDualUserTest extends KernelTestBase {
+
+  /**
+   * An anonymous user for testing purposes.
+   *
+   * @var \Drupal\user\Entity\User
+   */
+  protected $anonymous;
+
+  /**
+   * An authenticated user for testing purposes.
+   *
+   * @var \Drupal\user\Entity\User
+   */
+  protected $authenticated;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['system', 'user', 'condition_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->installSchema('system', 'sequences');
+    $this->installEntitySchema('user');
+
+    $this->anonymous = User::create(['uid' => 0]);
+    $this->authenticated = User::create(['uid' => 1]);
+  }
+
+  /**
+   * Tests the dual user condition.
+   */
+  public function testConditions() {
+    $this->doTestIdenticalUser();
+    $this->doTestDifferentUser();
+  }
+
+  /**
+   * Tests with both contexts mapped to the same user.
+   */
+  protected function doTestIdenticalUser() {
+    /** @var \Drupal\Core\Condition\ConditionPluginBase $condition */
+    $condition = \Drupal::service('plugin.manager.condition')
+      ->createInstance('condition_test_dual_user')
+      // Map the anonymous user to both contexts.
+      ->setContextMapping([
+        'user1' => 'anonymous',
+        'user2' => 'anonymous',
+      ]);
+    $definition = new ContextDefinition('entity:user');
+    $contexts['anonymous'] = (new Context($definition))->setContextValue($this->anonymous);
+    \Drupal::service('context.handler')->applyContextMapping($condition, $contexts);
+    $this->assertTrue($condition->execute());
+  }
+
+  /**
+   * Tests with each context mapped to different users.
+   */
+  protected function doTestDifferentUser() {
+    /** @var \Drupal\Core\Condition\ConditionPluginBase $condition */
+    $condition = \Drupal::service('plugin.manager.condition')
+      ->createInstance('condition_test_dual_user')
+      ->setContextMapping([
+        'user1' => 'anonymous',
+        'user2' => 'authenticated',
+      ]);
+    $definition = new ContextDefinition('entity:user');
+    $contexts['anonymous'] = (new Context($definition))->setContextValue($this->anonymous);
+    $contexts['authenticated'] = (new Context($definition))->setContextValue($this->authenticated);
+    \Drupal::service('context.handler')->applyContextMapping($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 b586c02..613c165 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/ContextHandlerTest.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/ContextHandlerTest.php
@@ -305,7 +305,7 @@ public function testApplyContextMappingConfigurableAssigned() {
       ->method('setContextValue')
       ->with('hit', array('foo'));
 
-    $this->contextHandler->applyContextMapping($plugin, $contexts, array('name' => 'hit'));
+    $this->contextHandler->applyContextMapping($plugin, $contexts, ['hit' => 'name']);
   }
 
   /**
@@ -333,7 +333,7 @@ public function testApplyContextMappingConfigurableAssignedMiss() {
     $plugin->expects($this->never())
       ->method('setContextValue');
 
-    $this->contextHandler->applyContextMapping($plugin, $contexts, array('name' => 'miss'));
+    $this->contextHandler->applyContextMapping($plugin, $contexts, ['miss' => 'name']);
   }
 
 }