diff --git a/wp-admin/includes/schema.php b/wp-admin/includes/schema.php
index 89d9fabfc0..d339af3b17 100644
--- a/wp-admin/includes/schema.php
+++ b/wp-admin/includes/schema.php
@@ -556,6 +556,9 @@ function populate_options( array $options = array() ) {
 
 		// 5.8.0
 		'wp_force_deactivated_plugins'    => array(),
+
+		// 6.4.0
+		'wp_attachment_pages_enabled'     => 0,
 	);
 
 	// 3.3.0
diff --git a/wp-admin/includes/upgrade.php b/wp-admin/includes/upgrade.php
index bf0b12405d..f4aac0e764 100644
--- a/wp-admin/includes/upgrade.php
+++ b/wp-admin/includes/upgrade.php
@@ -839,6 +839,10 @@ function upgrade_all() {
 		upgrade_630();
 	}
 
+	if ( $wp_current_db_version < 56657 ) {
+		upgrade_640();
+	}
+
 	maybe_disable_link_manager();
 
 	maybe_disable_automattic_widgets();
@@ -2322,6 +2326,23 @@ function upgrade_630() {
 	}
 }
 
+/**
+ * Executes changes made in WordPress 6.4.0.
+ *
+ * @ignore
+ * @since 6.4.0
+ *
+ * @global int $wp_current_db_version The old (current) database version.
+ */
+function upgrade_640() {
+	global $wp_current_db_version;
+
+	if ( $wp_current_db_version < 56657 ) {
+		// Enable attachment pages.
+		update_option( 'wp_media_use_attachment_pages', 1 );
+	}
+}
+
 /**
  * Executes network-level upgrade routines.
  *
diff --git a/wp-includes/canonical.php b/wp-includes/canonical.php
index 606973b31d..2f3cd68903 100644
--- a/wp-includes/canonical.php
+++ b/wp-includes/canonical.php
@@ -545,6 +545,18 @@ function redirect_canonical( $requested_url = null, $do_redirect = true ) {
 		}
 	}
 
+	$is_attachment_redirect = false;
+
+	if ( is_attachment() && ! get_option( 'wp_attachment_pages_enabled' ) ) {
+		$attachment_id = get_query_var( 'attachment_id' );
+
+		if ( current_user_can( 'read_post', $attachment_id ) ) {
+			$redirect_url = wp_get_attachment_url( $attachment_id );
+
+			$is_attachment_redirect = true;
+		}
+	}
+
 	$redirect['query'] = preg_replace( '#^\??&*?#', '', $redirect['query'] );
 
 	// Tack on any additional query vars.
@@ -650,6 +662,7 @@ function redirect_canonical( $requested_url = null, $do_redirect = true ) {
 
 	// Trailing slashes.
 	if ( is_object( $wp_rewrite ) && $wp_rewrite->using_permalinks()
+		&& ! $is_attachment_redirect
 		&& ! is_404() && ( ! is_front_page() || is_front_page() && get_query_var( 'paged' ) > 1 )
 	) {
 		$user_ts_type = '';
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 7c8e34c749..2920ba7159 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -16,14 +16,14 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.4-alpha-56656';
+$wp_version = '6.4-alpha-56657';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.
  *
  * @global int $wp_db_version
  */
-$wp_db_version = 55853;
+$wp_db_version = 56657;
 
 /**
  * Holds the TinyMCE version.