diff --git a/src/wp-includes/block-supports/elements.php b/src/wp-includes/block-supports/elements.php
index 770e3e95c3..4f3de8c5b8 100644
--- a/src/wp-includes/block-supports/elements.php
+++ b/src/wp-includes/block-supports/elements.php
@@ -36,6 +36,9 @@ function wp_render_elements_support( $block_content, $block ) {
 	}
 
 	$block_type = WP_Block_Type_Registry::get_instance()->get_registered( $block['blockName'] );
+	if ( ! $block_type ) {
+		return $block_content;
+	}
 
 	$element_color_properties = array(
 		'button'  => array(
diff --git a/tests/phpunit/tests/block-supports/wpRenderElementsSupport.php b/tests/phpunit/tests/block-supports/wpRenderElementsSupport.php
index a65f53b471..db5307d207 100644
--- a/tests/phpunit/tests/block-supports/wpRenderElementsSupport.php
+++ b/tests/phpunit/tests/block-supports/wpRenderElementsSupport.php
@@ -18,6 +18,39 @@ class Tests_Block_Supports_WpRenderElementsSupport extends WP_UnitTestCase {
 		parent::tear_down();
 	}
 
+	/**
+	 * Tests that block supports leaves block content alone if the block type
+	 * isn't registered.
+	 *
+	 * @ticket 59578
+	 *
+	 * @covers ::wp_render_elements_support
+	 *
+	 * @return void
+	 */
+	public function test_leaves_block_content_alone_when_block_type_not_registered() {
+		$block = array(
+			'blockName' => 'test/element-block-supports',
+			'attrs'     => array(
+				'style' => array(
+					'elements' => array(
+						'button' => array(
+							'color' => array(
+								'text'       => 'var:preset|color|vivid-red',
+								'background' => '#fff',
+							),
+						),
+					),
+				),
+			),
+		);
+
+		$block_markup = '<p>Hello <a href="http://www.wordpress.org/">WordPress</a>!</p>';
+		$actual       = wp_render_elements_support( $block_markup, $block );
+
+		$this->assertSame( $block_markup, $actual, 'Expected to leave block content unmodified, but found changes.' );
+	}
+
 	/**
 	 * Tests that elements block support applies the correct classname.
 	 *
@@ -64,7 +97,7 @@ class Tests_Block_Supports_WpRenderElementsSupport extends WP_UnitTestCase {
 		$this->assertMatchesRegularExpression(
 			$expected_markup,
 			$actual,
-			'Position block wrapper markup should be correct'
+			'Block wrapper markup should be correct'
 		);
 	}
 
@@ -80,6 +113,34 @@ class Tests_Block_Supports_WpRenderElementsSupport extends WP_UnitTestCase {
 		);
 
 		return array(
+			// @ticket 59578
+			'empty block markup remains untouched'         => array(
+				'color_settings'  => array(
+					'button' => true,
+				),
+				'elements_styles' => array(
+					'button' => array( 'color' => $color_styles ),
+				),
+				'block_markup'    => '',
+				'expected_markup' => '/^$/',
+			),
+			'empty block markup remains untouched when no block attributes' => array(
+				'color_settings'  => array(
+					'button' => true,
+				),
+				'elements_styles' => null,
+				'block_markup'    => '',
+				'expected_markup' => '/^$/',
+			),
+			'block markup remains untouched when block has no attributes' => array(
+				'color_settings'  => array(
+					'button' => true,
+				),
+				'elements_styles' => null,
+				'block_markup'    => '<p>Hello <a href="http://www.wordpress.org/">WordPress</a>!</p>',
+				'expected_markup' => '/^<p>Hello <a href="http:\/\/www.wordpress.org\/">WordPress<\/a>!<\/p>$/',
+			),
+			// @ticket 5418
 			'button element styles with serialization skipped' => array(
 				'color_settings'  => array(
 					'button'                          => true,