diff --git a/core/modules/block/tests/modules/block_test/src/Plugin/Condition/MissingSchema.php b/core/modules/block/tests/modules/block_test/src/Plugin/Condition/MissingSchema.php
new file mode 100644
index 0000000..977374c
--- /dev/null
+++ b/core/modules/block/tests/modules/block_test/src/Plugin/Condition/MissingSchema.php
@@ -0,0 +1,31 @@
+<?php
+
+namespace Drupal\block_test\Plugin\Condition;
+
+use Drupal\Core\Condition\ConditionPluginBase;
+
+/**
+ * Provides a 'missing_schema' condition.
+ *
+ * @Condition(
+ *   id = "missing_schema",
+ *   label = @Translation("Missing schema"),
+ * )
+ */
+class MissingSchema extends ConditionPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function evaluate() {
+    return FALSE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function summary() {
+    return 'Summary';
+  }
+
+}
diff --git a/core/modules/block/tests/src/Functional/BlockConditionTest.php b/core/modules/block/tests/src/Functional/BlockConditionTest.php
new file mode 100644
index 0000000..f29324a
--- /dev/null
+++ b/core/modules/block/tests/src/Functional/BlockConditionTest.php
@@ -0,0 +1,42 @@
+<?php
+
+namespace Drupal\Tests\block\Functional;
+
+use Drupal\Core\Url;
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests the interaction between blocks and conditions.
+ *
+ * @group block
+ */
+class BlockConditionTest extends BrowserTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['block_test'];
+
+  /**
+   * Tests that missing schema on a condition does not affect block visibility.
+   */
+  public function testMissingSchemaCondition() {
+    $this->drupalLogin($this->drupalCreateUser([
+      'access administration pages',
+      'administer blocks',
+      'view the administration theme',
+    ]));
+
+    // Initially the "Powered by" block does not exist.
+    $this->drupalGet('');
+    $this->assertSession()->pageTextNotContains('Powered by');
+
+    $this->drupalGet(Url::fromRoute('block.admin_add', ['plugin_id' => 'system_powered_by_block']));
+    $this->submitForm(['region' => 'content'], 'Save block');
+
+    // Now the "Powered by" block is shown.
+    $this->drupalGet('');
+    $this->assertSession()->pageTextContains('Powered by');
+  }
+
+}