diff --git a/lambda/dockerimagebuilder/__init__.py b/lambda/dockerimagebuilder/__init__.py
index dcda9f0..8589bb5 100644
--- a/lambda/dockerimagebuilder/__init__.py
+++ b/lambda/dockerimagebuilder/__init__.py
@@ -70,7 +70,7 @@ def handler(event: Dict[str, Any], context) -> Dict[str, Any]:  # type: ignore [
     try:
         instances = ec2_resource.create_instances(
             ImageId=ami_id,
-            SubnetId=os.environ["LISA_SUBNET_ID"],
+            SubnetId=os.environ.get("LISA_SUBNET_ID", None),
             MinCount=1,
             MaxCount=1,
             InstanceType="m5.large",