diff --git a/lib/blocks.php b/lib/blocks.php
index e30917096dcc5..8fecc848dd0e7 100644
--- a/lib/blocks.php
+++ b/lib/blocks.php
@@ -14,16 +14,18 @@
  *
  * @since 0.1.0
  *
- * @param string $name Block type name including namespace.
- * @param array  $args {
- *     Array of block type arguments. Any arguments may be defined, however the following
- *     ones are supported by default.
+ * @param string|WP_Block_Type $name Block type name including namespace, or alternatively a
+ *                                   complete WP_Block_Type instance. In case a WP_Block_Type
+ *                                   is provided, the $args parameter will be ignored.
+ * @param array                $args {
+ *     Optional. Array of block type arguments. Any arguments may be defined, however the
+ *     ones described below are supported by default. Default empty array.
  *
  *     @type callable $render Callback used to render blocks of this block type.
  * }
  * @return WP_Block_Type|false The registered block type on success, or false on failure.
  */
-function register_block_type( $name, $args ) {
+function register_block_type( $name, $args = array() ) {
 	return WP_Block_Type_Registry::get_instance()->register( $name, $args );
 }
 
diff --git a/lib/class-wp-block-type-registry.php b/lib/class-wp-block-type-registry.php
index d1c63d182b537..c4244f09b749b 100644
--- a/lib/class-wp-block-type-registry.php
+++ b/lib/class-wp-block-type-registry.php
@@ -37,16 +37,24 @@ final class WP_Block_Type_Registry {
 	 * @since 0.2.0
 	 * @access public
 	 *
-	 * @param string $name Block type name including namespace.
-	 * @param array  $args {
-	 *     Array of block type arguments. Any arguments may be defined, however the following
-	 *     ones are supported by default.
+	 * @param string|WP_Block_Type $name Block type name including namespace, or alternatively a
+	 *                                   complete WP_Block_Type instance. In case a WP_Block_Type
+	 *                                   is provided, the $args parameter will be ignored.
+	 * @param array                $args {
+	 *     Optional. Array of block type arguments. Any arguments may be defined, however the
+	 *     ones described below are supported by default. Default empty array.
 	 *
 	 *     @type callable $render Callback used to render blocks of this block type.
 	 * }
 	 * @return WP_Block_Type|false The registered block type on success, or false on failure.
 	 */
-	public function register( $name, $args ) {
+	public function register( $name, $args = array() ) {
+		$block_type = null;
+		if ( is_a( $name, 'WP_Block_Type' ) ) {
+			$block_type = $name;
+			$name = $block_type->name;
+		}
+
 		if ( ! is_string( $name ) ) {
 			$message = __( 'Block type names must be strings.' );
 			_doing_it_wrong( __METHOD__, $message, '0.1.0' );
@@ -67,7 +75,9 @@ public function register( $name, $args ) {
 			return false;
 		}
 
-		$block_type = new WP_Block_Type( $name, $args );
+		if ( ! $block_type ) {
+			$block_type = new WP_Block_Type( $name, $args );
+		}
 
 		$this->registered_block_types[ $name ] = $block_type;
 
diff --git a/lib/class-wp-block-type.php b/lib/class-wp-block-type.php
index 0193652352c05..a95a935f14186 100644
--- a/lib/class-wp-block-type.php
+++ b/lib/class-wp-block-type.php
@@ -13,7 +13,7 @@
  *
  * @see register_block_type()
  */
-final class WP_Block_Type {
+class WP_Block_Type {
 	/**
 	 * Block type key.
 	 *
diff --git a/phpunit/bootstrap.php b/phpunit/bootstrap.php
index cb97777e2b12f..ec5f74bad3115 100644
--- a/phpunit/bootstrap.php
+++ b/phpunit/bootstrap.php
@@ -32,6 +32,9 @@
  */
 function _manually_load_plugin() {
 	require dirname( dirname( __FILE__ ) ) . '/gutenberg.php';
+
+	// Require dummy block type class for testing.
+	require_once dirname( __FILE__ ) . '/class-wp-dummy-block-type.php';
 }
 tests_add_filter( 'muplugins_loaded', '_manually_load_plugin' );
 
diff --git a/phpunit/class-block-type-registry-test.php b/phpunit/class-block-type-registry-test.php
index 4fca2c54eb6f6..50f1550d8bbbb 100644
--- a/phpunit/class-block-type-registry-test.php
+++ b/phpunit/class-block-type-registry-test.php
@@ -91,6 +91,16 @@ function test_register_block_type_twice() {
 		$this->assertFalse( $result );
 	}
 
+	/**
+	 * Should accept a WP_Block_Type instance
+	 */
+	function test_register_block_type_instance() {
+		$block_type = new WP_Dummy_Block_Type( 'core/dummy' );
+
+		$result = $this->registry->register( $block_type );
+		$this->assertSame( $block_type, $result );
+	}
+
 	/**
 	 * Unregistering should fail if a block is not registered
 	 *
diff --git a/phpunit/class-wp-dummy-block-type.php b/phpunit/class-wp-dummy-block-type.php
new file mode 100644
index 0000000000000..cdd697872044a
--- /dev/null
+++ b/phpunit/class-wp-dummy-block-type.php
@@ -0,0 +1,16 @@
+<?php
+/**
+ * WP_Dummy_Block_Type for testing
+ *
+ * @package Gutenberg
+ */
+
+/**
+ * Test class extending WP_Block_Type
+ */
+class WP_Dummy_Block_Type extends WP_Block_Type {
+
+	public function render( $attributes = array(), $content = '' ) {
+		return '<div>' . $content . '</div>';
+	}
+}