Index: src/wp-includes/post.php
===================================================================
--- src/wp-includes/post.php	(revision 37315)
+++ src/wp-includes/post.php	(working copy)
@@ -4428,11 +4428,12 @@
  * Sub pages will be in the "directory" under the parent page post name.
  *
  * @since 1.5.0
+ * @since 4.6.0 The $page parameter is optional.
  *
- * @param WP_Post|object|int $page Page object or page ID.
+ * @param WP_Post|object|int $page Optional. Page ID or WP_Post object. Default is global $post.
  * @return string|false Page URI, false on error.
  */
-function get_page_uri( $page ) {
+function get_page_uri( $page = 0 ) {
 	if ( ! $page instanceof WP_Post ) {
 		$page = get_post( $page );
 	}
Index: tests/phpunit/tests/post/getPageUri.php
===================================================================
--- tests/phpunit/tests/post/getPageUri.php	(nonexistent)
+++ tests/phpunit/tests/post/getPageUri.php	(working copy)
@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * @group post
+ */
+
+class Tests_Post_getPageUri extends WP_UnitTestCase {
+
+	/**
+	 * @group f
+	 */
+	function test_get_page_uri_without_argument() {
+		$post_id = self::factory()->post->create(array(
+      'post_title' => 'Blood Orange announces summer tour dates',
+      'post_name' => 'blood-orange-announces-summer-tour-dates',
+    ));
+    $post = get_post( $post_id );
+		$this->go_to( get_permalink( $post_id ) );
+    $this->assertEquals( 'blood-orange-announces-summer-tour-dates', get_page_uri() );
+	}
+}