core/lib/Drupal/Core/Block/BlockBase.php           |  2 +-
 .../Drupal/Tests/Core/Block/BlockBaseTest.php      | 35 ++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/core/lib/Drupal/Core/Block/BlockBase.php b/core/lib/Drupal/Core/Block/BlockBase.php
index e21926a..8ca3e7c 100644
--- a/core/lib/Drupal/Core/Block/BlockBase.php
+++ b/core/lib/Drupal/Core/Block/BlockBase.php
@@ -280,7 +280,7 @@ public function getFormClass($operation) {
     if (isset($this->getPluginDefinition()['forms'][$operation])) {
       return $this->getPluginDefinition()['forms'][$operation];
     }
-    elseif ($operation === 'configure' && $this instanceof PluginFormInterface) {
+    elseif ($operation === 'configure') {
       return static::class;
     }
   }
diff --git a/core/tests/Drupal/Tests/Core/Block/BlockBaseTest.php b/core/tests/Drupal/Tests/Core/Block/BlockBaseTest.php
index 541c0c1..0e53b8f 100644
--- a/core/tests/Drupal/Tests/Core/Block/BlockBaseTest.php
+++ b/core/tests/Drupal/Tests/Core/Block/BlockBaseTest.php
@@ -3,6 +3,7 @@
 namespace Drupal\Tests\Core\Block;
 
 use Drupal\block_test\Plugin\Block\TestBlockInstantiation;
+use Drupal\Core\Block\BlockBase;
 use Drupal\Tests\UnitTestCase;
 
 /**
@@ -42,4 +43,38 @@ public function testGetMachineNameSuggestion() {
     $this->assertEquals('uberawesome', $block_base->getMachineNameSuggestion());
   }
 
+  /**
+   * @covers ::getFormClass
+   * @covers ::hasFormClass
+   * @dataProvider providerGetFormClass
+   */
+  public function testGetFormClass(BlockBase $block_plugin, $operation, $expected_class) {
+    $this->assertSame($expected_class, $block_plugin->getFormClass($operation));
+    $this->assertSame($expected_class !== NULL, $block_plugin->hasFormClass($operation));
+  }
+
+  /**
+   * @return array
+   */
+  public function providerGetFormClass() {
+    $block_plugin_without_forms = new TestBlockInstantiation([],  'block_plugin_without_forms', [
+      'provider' => 'block_test',
+    ]);
+    // A block plugin that has a form defined for the 'poke' operation.
+    $block_plugin_with_forms = new TestBlockInstantiation([], 'block_plugin_with_forms', [
+      'provider' => 'block_test',
+      'forms' => [
+        'poke' => static::class,
+      ],
+    ]);
+    return [
+      'block plugin without forms, "configure" operation' => [$block_plugin_without_forms, 'configure', TestBlockInstantiation::class],
+      'block plugin without forms, "tickle" operation'    => [$block_plugin_without_forms, 'tickle', NULL],
+      'block plugin withut forms, "poke" operation'       => [$block_plugin_without_forms, 'poke', NULL],
+      'block plugin with forms, "configure" operation' => [$block_plugin_with_forms, 'configure', TestBlockInstantiation::class],
+      'block plugin with forms, "tickle" operation'    => [$block_plugin_with_forms, 'tickle', NULL],
+      'block plugin with forms, "poke" operation'      => [$block_plugin_with_forms, 'poke', static::class],
+    ];
+  }
+
 }