diff --git src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php
index 059f78c6e8..2df517d32c 100644
--- src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php
+++ src/wp-includes/rest-api/fields/class-wp-rest-meta-fields.php
@@ -324,7 +324,7 @@ abstract class WP_REST_Meta_Fields {
 		$old_value = get_metadata( $meta_type, $object_id, $meta_key );
 
 		if ( 1 === count( $old_value ) ) {
-			if ( $old_value[0] === $meta_value ) {
+			if ( (string) sanitize_meta( $meta_key, wp_unslash( $meta_value ), $meta_type ) === $old_value[0] ) {
 				return true;
 			}
 		}
diff --git tests/phpunit/tests/rest-api/rest-post-meta-fields.php tests/phpunit/tests/rest-api/rest-post-meta-fields.php
index 2b09d994d1..77dba47b91 100644
--- tests/phpunit/tests/rest-api/rest-post-meta-fields.php
+++ tests/phpunit/tests/rest-api/rest-post-meta-fields.php
@@ -1255,6 +1255,88 @@ class WP_Test_REST_Post_Meta_Fields extends WP_Test_REST_TestCase {
 		return $data;
 	}
 
+	/**
+	 * @ticket 42069
+	 * @dataProvider data_update_value_return_success_with_same_value
+	 */
+	public function test_update_value_return_success_with_same_value( $meta_key, $meta_value ) {
+		register_meta(
+			'post',
+			$meta_key,
+			array(
+				'show_in_rest' => true,
+				'single'       => true,
+				'type'         => 'string',
+			)
+		);
+
+		add_post_meta( self::$post_id, $meta_key, $meta_value );
+
+		$this->grant_write_permission();
+
+		$data = array(
+			'meta' => array(
+				$meta_key => $meta_value,
+			),
+		);
+
+		$request = new WP_REST_Request( 'POST', sprintf( '/wp/v2/posts/%d', self::$post_id ) );
+		$request->set_body_params( $data );
+
+		$response = rest_get_server()->dispatch( $request );
+
+		$this->assertEquals( 200, $response->get_status() );
+	}
+
+	public function data_update_value_return_success_with_same_value() {
+		return array(
+			array( 'test_boolean_update', 0 ),
+			array( 'test_boolean_update', 1 ),
+			array( 'test_boolean_update', false ),
+			array( 'test_boolean_update', true ),
+			array( 'test_boolean_update', '' ),
+			array( 'test_boolean_update', '0' ),
+			array( 'test_boolean_update', '1' ),
+			array( 'test_textured_text_update', 'She said, "What about the > 10,000 penguins in the kitchen?"' ),
+			array( 'test_textured_text_update', "He's about to do something rash..." ),
+			array( 'test_json_encoded', json_encode( array( 'foo' => 'bar' ) ) ),
+		);
+	}
+
+	/**
+	 * @ticket 42069
+	 * @dataProvider data_update_value_return_success_with_similar_value
+	 */
+	public function test_update_value_return_success_with_similar_value( $meta_key, $meta_value, $update_meta_value ) {
+		add_post_meta( self::$post_id, $meta_key, $meta_value );
+
+		$this->grant_write_permission();
+
+		$data = array(
+			'meta' => array(
+				$meta_key => $update_meta_value,
+			),
+		);
+
+		$request = new WP_REST_Request( 'POST', sprintf( '/wp/v2/posts/%d', self::$post_id ) );
+		$request->set_body_params( $data );
+
+		$response = rest_get_server()->dispatch( $request );
+
+		$this->assertEquals( 200, $response->get_status() );
+	}
+
+	public function data_update_value_return_success_with_similar_value() {
+		return array(
+			array( 'test_boolean_update', 0, '' ),
+			array( 'test_boolean_update', 1, '1' ),
+			array( 'test_boolean_update', false, 0 ),
+			array( 'test_boolean_update', true, 1 ),
+			array( 'test_boolean_update', '', false ),
+			array( 'test_boolean_update', '1', true ),
+		);
+	}
+
 	/**
 	 * Internal function used to disable an insert query which
 	 * will trigger a wpdb error for testing purposes.