diff --git a/splitio_platform_interface/lib/split_result.dart b/splitio_platform_interface/lib/split_result.dart
index 80b452b..f1c0896 100644
--- a/splitio_platform_interface/lib/split_result.dart
+++ b/splitio_platform_interface/lib/split_result.dart
@@ -13,8 +13,8 @@ class SplitResult {
   String toString() {
     return '{"treatment": "' +
         treatment +
-        '", config: "' +
-        (config ?? 'null') +
-        '"}';
+        '", config: ' +
+        (config != null ? '"$config"' : 'null') +
+        '}';
   }
 }