diff --git a/src/Builders/Paths/Operation/ParametersBuilder.php b/src/Builders/Paths/Operation/ParametersBuilder.php
index 2333690..9d376fc 100644
--- a/src/Builders/Paths/Operation/ParametersBuilder.php
+++ b/src/Builders/Paths/Operation/ParametersBuilder.php
@@ -39,7 +39,9 @@ protected function buildPath(RouteInformation $route): Collection
                         return null;
                     }
 
-                    $schema = SchemaHelpers::guessFromReflectionType($reflectionParameter->getType());
+                    if ($reflectionParameter->getType() instanceof \ReflectionNamedType) {
+                        $schema = SchemaHelpers::guessFromReflectionType($reflectionParameter->getType());
+                    }
                 }
 
                 /** @var Param $description */