diff --git a/tempest/tempest_ext.conf b/tempest/tempest_ext.conf
index 84bc6e2..d4777f2 100644
--- a/tempest/tempest_ext.conf
+++ b/tempest/tempest_ext.conf
@@ -28,7 +28,7 @@
 minimal_instance_type = m1.tiny
 network_for_ssh = net_name
 floating_network_name = net_name
-fixed_subnet_name = fixed-subnet
+fixed_subnet_name = ${FIXED_SUBNET_NAME}
 disable_ssl_certificate_validation = True
 image_ref = ${IMAGE_REF2}
 minimal_image_ref = ${IMAGE_REF2}