diff --git a/agents/s01_agent_loop.py b/agents/s01_agent_loop.py
index 3e6c9133d..adf879b18 100644
--- a/agents/s01_agent_loop.py
+++ b/agents/s01_agent_loop.py
@@ -31,7 +31,7 @@
 
 load_dotenv(override=True)
 
-if os.getenv("ANTHROPIC_BASE_URL"):
+if os.getenv("ANTHROPIC_BASE_URL") is not None:
     os.environ.pop("ANTHROPIC_AUTH_TOKEN", None)
 
 client = Anthropic(base_url=os.getenv("ANTHROPIC_BASE_URL"))