diff --git a/src/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php b/src/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php
index 8f540789c6..52e8fcf0cd 100644
--- a/src/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php
+++ b/src/wp-includes/rest-api/endpoints/class-wp-rest-users-controller.php
@@ -725,7 +725,10 @@ class WP_REST_Users_Controller extends WP_REST_Controller {
 			);
 		}
 
-		$owner_id = email_exists( $request['email'] );
+		$owner_id = false;
+		if ( is_string( $request['email'] ) ) {
+			$owner_id = email_exists( $request['email'] );
+		}
 
 		if ( $owner_id && $owner_id !== $id ) {
 			return new WP_Error(