diff --git a/lib/oto/pipeline/pipeline_condition.dart b/lib/oto/pipeline/pipeline_condition.dart
index 1f1d55d..77eccb0 100644
--- a/lib/oto/pipeline/pipeline_condition.dart
+++ b/lib/oto/pipeline/pipeline_condition.dart
@@ -33,7 +33,7 @@ abstract class PipelineCondition extends PipelineExecutor {
           : (value is String)
               ? double.parse(value) as double?
               : value,
-      'string': (value) => (value == 'null' || value == null) ? null : value,
+      'string': (value) => (value == 'null' || value == null) ? null : value.toString(),
       'bool': (value) => (value == 'null' || value == null)
           ? null
           : (value is String)