diff --git a/src/Preparator/Error400BadTypesPreparator.php b/src/Preparator/Error400BadTypesPreparator.php
index 142654f..1209ae2 100644
--- a/src/Preparator/Error400BadTypesPreparator.php
+++ b/src/Preparator/Error400BadTypesPreparator.php
@@ -84,7 +84,7 @@ protected function prepareForBodyFields(Body $body, array $parameters, Operation
         /** @var Schema $schema */
         foreach ($body->getSchema()->properties as $property => $schema) {
             foreach (self::SCHEMA_TYPES as $type) {
-                if ($this->isAllowedType($schema->type, $type)) {
+                if ($this->isAllowedType($schema->type ?? '', $type)) {
                     continue;
                 }