Index: src/wp-includes/comment.php
===================================================================
--- src/wp-includes/comment.php	(revision 27052)
+++ src/wp-includes/comment.php	(working copy)
@@ -909,7 +909,7 @@
 	if ( null === $comments && null === $per_page && null === $threaded && !empty($wp_query->max_num_comment_pages) )
 		return $wp_query->max_num_comment_pages;
 
-	if ( !$comments || !is_array($comments) )
+	if ( ( ! $comments || ! is_array( $comments ) ) && ! empty( $wp_query->comments )  )
 		$comments = $wp_query->comments;
 
 	if ( empty($comments) )
Index: tests/phpunit/tests/comment/getCommentsPagesCount.php
===================================================================
--- tests/phpunit/tests/comment/getCommentsPagesCount.php	(revision 0)
+++ tests/phpunit/tests/comment/getCommentsPagesCount.php	(working copy)
@@ -0,0 +1,170 @@
+<?php
+/**
+ * Validate the logic of get_comments_pages_count
+ * @group comment
+ */
+class Tests_Comment_GetCommentsPagesCount extends WP_UnitTestCase {
+	protected $option_page_comments;
+	protected $option_comments_per_page;
+	protected $option_thread_comments;
+	protected $option_posts_per_rss;
+
+	/**
+	 * setUp options
+	 */
+	function setUp() {
+		parent::setUp();
+		$this->option_page_comments = get_option( 'page_comments' );
+		$this->option_page_comments = get_option( 'comments_per_page' );
+		$this->option_page_comments = get_option( 'thread_comments' );
+		$this->option_posts_per_rss = get_option( 'posts_per_rss' );
+
+		update_option( 'page_comments', true );
+	}
+
+	/**
+	 * tearDown options
+	 */
+	function tearDown() {
+		parent::tearDown();
+		update_option( 'page_comments', $this->option_page_comments );
+		update_option( 'comments_per_page', $this->option_page_comments );
+		update_option( 'thread_comments', $this->option_page_comments );
+		update_option( 'posts_per_rss', $this->option_posts_per_rss );
+	}
+
+	/**
+	 * Validate get_comments_pages_count for empty comments
+	 */
+	function test_empty() {
+		//setup post and comments
+		$post_id = $this->factory->post->create( array( 'post_title' => 'comment--post', 'post_type' => 'post' ) );
+		$this->go_to( '/?p=' . $post_id );
+
+		global $wp_query;
+		unset( $wp_query->comments );
+
+		$comments = get_comments( array( 'post_id' => $post_id ) );
+
+		$this->assertEquals( 0, get_comment_pages_count( $comments, 10, false ) );
+		$this->assertEquals( 0, get_comment_pages_count( $comments, 1, false ) );
+		$this->assertEquals( 0, get_comment_pages_count( $comments, 0, false ) );
+		$this->assertEquals( 0, get_comment_pages_count( $comments, 10, true ) );
+		$this->assertEquals( 0, get_comment_pages_count( $comments, 5 ) );
+		$this->assertEquals( 0, get_comment_pages_count( $comments ) );
+		$this->assertequals( 0, get_comment_pages_count( null, 1 ) );
+	}
+
+	/**
+	 * Validate get_comments_pages_count for treaded comments
+	 */
+	function test_threaded_comments( ) {
+		//setup post and comments
+		$post = $this->factory->post->create_and_get( array( 'post_title' => 'comment--post', 'post_type' => 'post' ) );
+		$comments = $this->factory->comment->create_post_comments( $post->ID, 15 );
+		$this->factory->comment->create_post_comments( $post->ID, 6, array( 'comment_parent' => $comments[0] ) );
+		$comments = get_comments( array( 'post_id' => $post->ID ) );
+
+		$this->assertEquals( 3, get_comment_pages_count( $comments, 10, false ) );
+		$this->assertEquals( 2, get_comment_pages_count( $comments, 10, true ) );
+		$this->assertEquals( 4, get_comment_pages_count( $comments, 4, true ) );
+	}
+
+	/**
+	 * Validate get_comments_pages_count for option page_comments
+	 */
+	function test_option_page_comments() {
+		//setup post and comments
+		$post = $this->factory->post->create_and_get( array( 'post_title' => 'comment--post', 'post_type' => 'post' ) );
+		$comments = $this->factory->comment->create_post_comments( $post->ID, 15 );
+
+		// comment paging disabled
+		update_option( 'page_comments', false );
+
+		$this->assertEquals( 1, get_comment_pages_count( $comments, 10, false ) );
+		$this->assertEquals( 1, get_comment_pages_count( $comments, 0, true ) );
+		$this->assertEquals( 1, get_comment_pages_count( $comments, 2, true ) );
+
+		// comment paging enabled
+		update_option( 'page_comments', true );
+
+		$this->assertEquals( 2, get_comment_pages_count( $comments, 10, false ) );
+		$this->assertEquals( 3, get_comment_pages_count( $comments, 5, false ) );
+	}
+
+	/**
+	 * Validate get_comments_pages_count for option tread_comments
+	 */
+	function test_option_thread_comments() {
+
+		//setup post and comments
+		$post = $this->factory->post->create_and_get( array( 'post_title' => 'comment--post', 'post_type' => 'post' ) );
+		$comments = $this->factory->comment->create_post_comments( $post->ID, 15 );
+		$this->factory->comment->create_post_comments( $post->ID, 6, array('comment_parent' => $comments[0] ) );
+		$comments = get_comments( array( 'post_id' => $post->ID ) );
+
+		update_option( 'thread_comments', false );
+
+		$this->assertEquals( 3, get_comment_pages_count( $comments, 10, false ) );
+		$this->assertEquals( 2, get_comment_pages_count( $comments, 10, true ) );
+		$this->assertEquals( 3, get_comment_pages_count( $comments, 10, null ) );
+		$this->assertEquals( 3, get_comment_pages_count( $comments, 10 ) );
+
+		update_option( 'thread_comments', true );
+
+		$this->assertEquals( 3, get_comment_pages_count( $comments, 10, false ) );
+		$this->assertEquals( 2, get_comment_pages_count( $comments, 10, true ) );
+		$this->assertEquals( 2, get_comment_pages_count( $comments, 10, null ) );
+		$this->assertEquals( 2, get_comment_pages_count( $comments, 10 ) );
+	}
+
+	/**
+	 * Validate $wp_query logic of get_comment_pages_count
+	 */
+	function test_wp_query_comments_per_page() {
+		global $wp_query;
+
+		update_option( 'posts_per_rss', 100 );
+
+		$post = $this->factory->post->create_and_get( array( 'post_title' => 'comment-post', 'post_type' => 'post' ) );
+		$comments = $this->factory->comment->create_post_comments( $post->ID, 25 );
+
+		$wp_query = new WP_Query( array( 'p' => $post->ID, 'comments_per_page' => 10, 'feed' =>'comments-' ) );
+
+		update_option( 'comments_per_page', 25 );
+
+		$this->assertEquals( 3, get_comment_pages_count() );
+		$this->assertEquals( 2, get_comment_pages_count( null, 20 ) );
+
+		$wp_query = new WP_Query( array( 'p' => $post->ID,'comments_per_page' => null, 'feed' =>'comments-' ) );
+
+		$this->assertEquals( 1, get_comment_pages_count() );
+		$this->assertEquals( 5, get_comment_pages_count( null, 5 ) );
+
+		$wp_query->query_vars['comments_per_page'] = null;
+
+		update_option( 'comments_per_page', 5 );
+
+		$this->assertEquals( 5, get_comment_pages_count() );
+		$this->assertEquals( 3, get_comment_pages_count( null, 11 ) );
+		$this->assertEquals( 5, get_comment_pages_count( null, 0 ) );
+	}
+
+	/**
+	 * Validate max_num_comment_pages logic of get_comment_pages_count
+	 */
+	 function test_max_num_comment_pages() {
+		global $wp_query;
+		$wp_query = new WP_Query();
+
+		$org_max_num_comment_pages = $wp_query->max_num_comment_pages;
+
+		$wp_query->max_num_comment_pages = 7;
+
+		$this->assertEquals( 7, get_comment_pages_count() );
+		$this->assertEquals( 7, get_comment_pages_count( null, null, null ) );
+		$this->assertEquals( 0, get_comment_pages_count( array(), null, null ) );
+
+		$wp_query->max_num_comment_pages = $org_max_num_comment_pages;
+	 }
+}
\ No newline at end of file