diff --git a/core/lib/Drupal/Component/Plugin/PluginBase.php b/core/lib/Drupal/Component/Plugin/PluginBase.php
index 8c3f274..fcd90bf 100644
--- a/core/lib/Drupal/Component/Plugin/PluginBase.php
+++ b/core/lib/Drupal/Component/Plugin/PluginBase.php
@@ -12,6 +12,11 @@
 abstract class PluginBase implements PluginInspectionInterface, DerivativeInspectionInterface {
 
   /**
+   * A string which is used to separate base plugin IDs from the derivative ID.
+   */
+  const DERIVATIVE_SEPARATOR = ':';
+
+  /**
    * The plugin_id.
    *
    * @var string
@@ -60,8 +65,8 @@ public function getPluginId() {
    */
   public function getBasePluginId() {
     $plugin_id = $this->getPluginId();
-    if (strpos($plugin_id, ':')) {
-      list($plugin_id) = explode(':', $plugin_id, 2);
+    if (strpos($plugin_id, static::DERIVATIVE_SEPARATOR)) {
+      list($plugin_id) = explode(static::DERIVATIVE_SEPARATOR, $plugin_id, 2);
     }
     return $plugin_id;
   }
@@ -72,8 +77,8 @@ public function getBasePluginId() {
   public function getDerivativeId() {
     $plugin_id = $this->getPluginId();
     $derivative_id = NULL;
-    if (strpos($plugin_id, ':')) {
-      list(, $derivative_id) = explode(':', $plugin_id, 2);
+    if (strpos($plugin_id, static::DERIVATIVE_SEPARATOR)) {
+      list(, $derivative_id) = explode(static::DERIVATIVE_SEPARATOR, $plugin_id, 2);
     }
     return $derivative_id;
   }
diff --git a/core/modules/block/lib/Drupal/block/Tests/BlockPreprocessUnitTest.php b/core/modules/block/lib/Drupal/block/Tests/BlockPreprocessUnitTest.php
index c399879..e343019 100644
--- a/core/modules/block/lib/Drupal/block/Tests/BlockPreprocessUnitTest.php
+++ b/core/modules/block/lib/Drupal/block/Tests/BlockPreprocessUnitTest.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\block\Tests\BlockPreprocessTest.
+ * Contains \Drupal\block\Tests\BlockPreprocessUnitTest.
  */
 
 namespace Drupal\block\Tests;
@@ -12,7 +12,7 @@
 /**
  * Web tests for template_preprocess_block().
  */
-class BlockPreprocessTest extends WebTestBase {
+class BlockPreprocessUnitTest extends WebTestBase {
 
   /**
    * Modules to enable.