diff --git a/src/wp-includes/class-wp-query.php b/src/wp-includes/class-wp-query.php
index 06d531c39a..6508e7f64e 100644
--- a/src/wp-includes/class-wp-query.php
+++ b/src/wp-includes/class-wp-query.php
@@ -3235,10 +3235,12 @@ class WP_Query {
 			 *
 			 * @since 2.1.0
 			 *
-			 * @param string   $found_posts The query to run to find the found posts.
-			 * @param WP_Query $this        The WP_Query instance (passed by reference).
+			 * @param string   $found_posts_query The query to run to find the found posts.
+			 * @param WP_Query $this              The WP_Query instance (passed by reference).
 			 */
-			$this->found_posts = $wpdb->get_var( apply_filters_ref_array( 'found_posts_query', array( 'SELECT FOUND_ROWS()', &$this ) ) );
+			$found_posts_query = apply_filters_ref_array( 'found_posts_query', array( 'SELECT FOUND_ROWS()', &$this ) );
+
+			$this->found_posts = (int) $wpdb->get_var( $found_posts_query );
 		} else {
 			if ( is_array( $this->posts ) ) {
 				$this->found_posts = count( $this->posts );
@@ -3259,7 +3261,7 @@ class WP_Query {
 		 * @param int      $found_posts The number of posts found.
 		 * @param WP_Query $this        The WP_Query instance (passed by reference).
 		 */
-		$this->found_posts = apply_filters_ref_array( 'found_posts', array( $this->found_posts, &$this ) );
+		$this->found_posts = (int) apply_filters_ref_array( 'found_posts', array( $this->found_posts, &$this ) );
 
 		if ( ! empty( $limits ) ) {
 			$this->max_num_pages = ceil( $this->found_posts / $q['posts_per_page'] );
diff --git a/tests/phpunit/tests/post/query.php b/tests/phpunit/tests/post/query.php
index 0659f2d613..5f131f5200 100644
--- a/tests/phpunit/tests/post/query.php
+++ b/tests/phpunit/tests/post/query.php
@@ -652,12 +652,14 @@ class Tests_Post_Query extends WP_UnitTestCase {
 		}
 
 		add_filter( 'split_the_query', '__return_true' );
+
 		$q = new WP_Query(
 			array(
 				'post_type'      => 'wptests_pt',
 				'posts_per_page' => 1,
 			)
 		);
+
 		remove_filter( 'split_the_query', '__return_true' );
 
 		$this->assertEquals( 2, $q->found_posts );
@@ -677,12 +679,14 @@ class Tests_Post_Query extends WP_UnitTestCase {
 
 		// ! $split_the_query
 		add_filter( 'split_the_query', '__return_false' );
+
 		$q = new WP_Query(
 			array(
 				'post_type'      => 'wptests_pt',
 				'posts_per_page' => 1,
 			)
 		);
+
 		remove_filter( 'split_the_query', '__return_false' );
 
 		$this->assertEquals( 2, $q->found_posts );
@@ -721,4 +725,37 @@ class Tests_Post_Query extends WP_UnitTestCase {
 		$this->assertEquals( $expected, $q->found_posts );
 	}
 
+	/**
+	 * @ticket 42469
+	 */
+	public function test_found_posts_should_be_integer_not_string() {
+		$this->post_id = self::factory()->post->create();
+
+		$q = new WP_Query(
+			array(
+				'posts_per_page' => 1,
+			)
+		);
+
+		$this->assertInternalType( 'int', $q->found_posts );
+	}
+
+	/**
+	 * @ticket 42469
+	 */
+	public function test_found_posts_should_be_integer_even_if_found_posts_filter_returns_string_value() {
+		$this->post_id = self::factory()->post->create();
+
+		add_filter( 'found_posts', '__return_empty_string' );
+
+		$q = new WP_Query(
+			array(
+				'posts_per_page' => 1,
+			)
+		);
+
+		remove_filter( 'found_posts', '__return_empty_string' );
+
+		$this->assertInternalType( 'int', $q->found_posts );
+	}
 }