If I try to call $this->get_post_type inside a filter function, I get a 502 bad gateway error.

505-bad-gateway.diff

diff --git a/lib/class-wp-json-posts.php b/lib/class-wp-json-posts.php
index 941c796..599e8af 100644
--- a/lib/class-wp-json-posts.php
+++ b/lib/class-wp-json-posts.php
@@ -1090,6 +1090,23 @@ class WP_JSON_Posts {
 	}
 
 	/**
+	 * Embed post type data into taxonomy data
+	 *
+	 * @uses self::get_post_type()
+	 * @param array $data Taxonomy data
+	 * @param array $taxonomy Internal taxonomy data
+	 * @return array Filtered data
+	 */
+	public function add_post_type_data( $data, $taxonomy ) {
+		foreach( $taxonomy->object_type as $type ) {
+			// $data['types'][ $type ] = $type; // This works
+			$data['types'][ $type ] = $this->get_post_type( $type ); // This doesn't: Why?
+		}
+
+		return $data;
+	}
+
+	/**
 	 * Helper method for {@see new_post} and {@see edit_post}, containing shared logic.
 	 *
 	 * @since 3.4.0
diff --git a/lib/class-wp-json-taxonomies.php b/lib/class-wp-json-taxonomies.php
index 4ca4767..539ea29 100644
--- a/lib/class-wp-json-taxonomies.php
+++ b/lib/class-wp-json-taxonomies.php
@@ -105,7 +105,7 @@ class WP_JSON_Taxonomies {
 			$data['meta']['links']['collection'] = json_url( $base_url );
 		}
 
-		return apply_filters( 'json_prepare_taxonomy', $data );
+		return apply_filters( 'json_prepare_taxonomy', $data, $taxonomy );
 	}
 
 	/**
diff --git a/plugin.php b/plugin.php
index 3571b04..dad44dc 100644
--- a/plugin.php
+++ b/plugin.php
@@ -75,6 +75,7 @@ function json_api_default_filters($server) {
 	// Posts
 	$wp_json_posts = new WP_JSON_Posts($server);
 	add_filter( 'json_endpoints', array( $wp_json_posts, 'register_routes' ), 0 );
+	add_filter( 'json_prepare_taxonomy', array( $wp_json_posts, 'add_post_type_data' ), 10, 2 );
 
 	// Users
 	$wp_json_users = new WP_JSON_Users($server);