diff --git a/features/openapi/docs.feature b/features/openapi/docs.feature
index 18f09998c8b..ae109da6012 100644
--- a/features/openapi/docs.feature
+++ b/features/openapi/docs.feature
@@ -238,7 +238,8 @@ Feature: Documentation support
                                         "type": "string"
                                     },
                                     "property": {
-                                        "type": ["string", "null"]
+                                        "type": "string",
+                                        "nullable": true
                                     },
                                     "required": {
                                         "type": "boolean"
diff --git a/src/Hydra/JsonSchema/SchemaFactory.php b/src/Hydra/JsonSchema/SchemaFactory.php
index 540834d92f5..30c41e01f30 100644
--- a/src/Hydra/JsonSchema/SchemaFactory.php
+++ b/src/Hydra/JsonSchema/SchemaFactory.php
@@ -92,12 +92,12 @@ public function buildSchema(string $className, string $format = 'jsonld', string
             unset($schema['items']);
 
             switch ($schema->getVersion()) {
-                // JSON Schema + OpenAPI 3.1
                 case Schema::VERSION_OPENAPI:
+                    $nullableStringDefinition = ['type' => 'string', 'nullable' => true];
+                    break;
                 case Schema::VERSION_JSON_SCHEMA:
                     $nullableStringDefinition = ['type' => ['string', 'null']];
                     break;
-                    // Swagger
                 default:
                     $nullableStringDefinition = ['type' => 'string'];
                     break;