diff --git a/vertexai/preview/reasoning_engines/templates/adk.py b/vertexai/preview/reasoning_engines/templates/adk.py
index a74e1bb6e6..eefe01ed53 100644
--- a/vertexai/preview/reasoning_engines/templates/adk.py
+++ b/vertexai/preview/reasoning_engines/templates/adk.py
@@ -491,7 +491,7 @@ def __init__(
         *,
         agent: "BaseAgent",
         plugins: Optional[List["BasePlugin"]] = None,
-        enable_tracing: bool = False,
+        enable_tracing: Optional[bool] = None,
         session_service_builder: Optional[Callable[..., "BaseSessionService"]] = None,
         artifact_service_builder: Optional[Callable[..., "BaseArtifactService"]] = None,
         memory_service_builder: Optional[Callable[..., "BaseMemoryService"]] = None,