diff --git a/includes/collection/class-users.php b/includes/collection/class-users.php
index 62b4264..506722b 100644
--- a/includes/collection/class-users.php
+++ b/includes/collection/class-users.php
@@ -7,6 +7,8 @@ use Activitypub\Model\User;
 use Activitypub\Model\Blog_User;
 use Activitypub\Model\Application_User;
 
+use function Activitypub\is_user_disabled;
+
 class Users {
 	/**
 	 * The ID of the Blog User
@@ -34,6 +36,14 @@ class Users {
 			$user_id = (int) $user_id;
 		}
 
+		if ( is_user_disabled( $user_id ) ) {
+			return new WP_Error(
+				'activitypub_user_not_found',
+				\__( 'User not found', 'activitypub' ),
+				array( 'status' => 404 )
+			);
+		}
+
 		if ( self::BLOG_USER_ID === $user_id ) {
 			return Blog_User::from_wp_user( $user_id );
 		} elseif ( self::APPLICATION_USER_ID === $user_id ) {
diff --git a/includes/functions.php b/includes/functions.php
index 15a769e..9d2a03e 100644
--- a/includes/functions.php
+++ b/includes/functions.php
@@ -299,6 +299,11 @@ function is_user_disabled( $user_id ) {
 			break;
 		// if the user is any other user, it's enabled if it can publish posts.
 		default:
+			if ( ! \get_user_by( 'id', $user_id ) ) {
+				$return = true;
+				break;
+			}
+
 			if ( defined( 'ACTIVITYPUB_DISABLE_USER' ) ) {
 				$return = ACTIVITYPUB_DISABLE_USER;
 				break;
diff --git a/includes/model/class-user.php b/includes/model/class-user.php
index d641497..23cd013 100644
--- a/includes/model/class-user.php
+++ b/includes/model/class-user.php
@@ -26,10 +26,7 @@ class User extends Actor {
 	protected $type = 'Person';
 
 	public static function from_wp_user( $user_id ) {
-		if (
-			is_user_disabled( $user_id ) ||
-			! get_user_by( 'id', $user_id )
-		) {
+		if ( is_user_disabled( $user_id ) ) {
 			return new WP_Error(
 				'activitypub_user_not_found',
 				\__( 'User not found', 'activitypub' ),
diff --git a/includes/rest/class-inbox.php b/includes/rest/class-inbox.php
index b530a37..98b4e55 100644
--- a/includes/rest/class-inbox.php
+++ b/includes/rest/class-inbox.php
@@ -124,7 +124,6 @@ class Inbox {
 	 * @return WP_REST_Response
 	 */
 	public static function user_inbox_post( $request ) {
-
 		$user_id = $request->get_param( 'user_id' );
 		$user    = User_Collection::get_by_various( $user_id );
 
@@ -150,7 +149,6 @@ class Inbox {
 	 * @return WP_REST_Response
 	 */
 	public static function shared_inbox_post( $request ) {
-
 		$data = $request->get_params();
 		$type = $request->get_param( 'type' );
 		$users = self::extract_recipients( $data );