diff --git a/src/hera/workflows/workflow.py b/src/hera/workflows/workflow.py
index ad37932e2..7752633fe 100644
--- a/src/hera/workflows/workflow.py
+++ b/src/hera/workflows/workflow.py
@@ -248,12 +248,12 @@ def _build_templates(self) -> Optional[List[TTemplate]]:
     arguments: Annotated[
         ArgumentsT,
         _WorkflowModelMapper("spec.arguments", ArgumentsMixin._build_arguments),
-    ]
+    ] = None
     metrics: Annotated[
         MetricsT,
         _WorkflowModelMapper("spec.metrics", MetricsMixin._build_metrics),
-    ]
-    volumes: Annotated[VolumesT, _WorkflowModelMapper("spec.volumes", VolumeMixin._build_volumes)]
+    ] = None
+    volumes: Annotated[VolumesT, _WorkflowModelMapper("spec.volumes", VolumeMixin._build_volumes)] = None
 
     # Hera-specific fields
     workflows_service: Optional[WorkflowsService] = None