diff --git a/src/Writing/PostmanCollectionWriter.php b/src/Writing/PostmanCollectionWriter.php
index 29be7765..691ff97a 100644
--- a/src/Writing/PostmanCollectionWriter.php
+++ b/src/Writing/PostmanCollectionWriter.php
@@ -222,7 +222,7 @@ protected function getFormDataParams(array $paramsKeyValue, ?string $key = null,
             if (!is_array($value)) {
                 $body[] = [
                     'key' => $index,
-                    'value' => $value,
+                    'value' => (string) $value,
                     'type' => 'text',
                     'description' => $paramsFullDetails[$index]->description ?? '',
                 ];