diff --git a/src/wp-includes/class-wp.php b/src/wp-includes/class-wp.php
index f1664747d4042..6f05a5fdd7e69 100644
--- a/src/wp-includes/class-wp.php
+++ b/src/wp-includes/class-wp.php
@@ -382,7 +382,10 @@ public function parse_request( $extra_query_vars = '' ) {
 					unset( $this->query_vars['post_type'] );
 				}
 			} else {
-				$this->query_vars['post_type'] = array_intersect( $this->query_vars['post_type'], $queryable_post_types );
+				$this->query_vars['post_type'] = array_intersect(
+					array_filter( $this->query_vars['post_type'], 'is_scalar' ),
+					$queryable_post_types
+				);
 			}
 		}
 
diff --git a/tests/phpunit/tests/wp/parseRequest.php b/tests/phpunit/tests/wp/parseRequest.php
index a34a873e892fb..68b2e6c42c222 100644
--- a/tests/phpunit/tests/wp/parseRequest.php
+++ b/tests/phpunit/tests/wp/parseRequest.php
@@ -56,4 +56,52 @@ static function ( $url ) {
 		$this->wp->parse_request();
 		$this->assertSame( '', $this->wp->request );
 	}
+
+	/**
+	 * @ticket 65123
+	 * @dataProvider data_parse_request_ignores_non_scalar_post_type_values
+	 */
+	public function test_parse_request_ignores_non_scalar_post_type_values( $request_method, $request_uri ) {
+		$original_get     = $_GET;
+		$original_post    = $_POST;
+		$original_request = $_SERVER['REQUEST_URI'] ?? null;
+		$original_self    = $_SERVER['PHP_SELF'] ?? null;
+
+		if ( 'GET' === $request_method ) {
+			$_GET['post_type'] = array( array( 'page' ), 'post' );
+		} else {
+			$_POST['post_type'] = array( array( 'page' ), 'post' );
+		}
+
+		$_SERVER['REQUEST_URI'] = $request_uri;
+		$_SERVER['PHP_SELF']    = '/index.php';
+
+		try {
+			$this->wp->parse_request();
+
+			$this->assertSame( array( 'post' ), array_values( $this->wp->query_vars['post_type'] ) );
+		} finally {
+			$_GET  = $original_get;
+			$_POST = $original_post;
+
+			if ( null === $original_request ) {
+				unset( $_SERVER['REQUEST_URI'] );
+			} else {
+				$_SERVER['REQUEST_URI'] = $original_request;
+			}
+
+			if ( null === $original_self ) {
+				unset( $_SERVER['PHP_SELF'] );
+			} else {
+				$_SERVER['PHP_SELF'] = $original_self;
+			}
+		}
+	}
+
+	public function data_parse_request_ignores_non_scalar_post_type_values() {
+		return array(
+			'get'  => array( 'GET', '/?post_type[][]=page&post_type[]=post' ),
+			'post' => array( 'POST', '/' ),
+		);
+	}
 }