diff --git a/defaults/main.yml b/defaults/main.yml
index 6fe886c3..0ef5f825 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -49,7 +49,7 @@ tempest_test_accounts: ""
 tempest_test_accounts_file_path: "{{ tempest_workspace }}/etc/tempest_accounts.yaml"
 # tempest_create_isolated_networks has an effect only when use_dynamic_credentials is enabled
 tempest_create_isolated_networks: true
-# tempest_fixed_network_name has an effect only when tempest_create_isolated_networks is disabled
+# tempest_fixed_network_name does not have an effect when dynamic credentials are used together with tempest_create_isolated_networks
 tempest_fixed_network_name: public
 
 # Tempest Resources
diff --git a/templates/tempest.conf.j2 b/templates/tempest.conf.j2
index 31b4781c..6dcdea4a 100644
--- a/templates/tempest.conf.j2
+++ b/templates/tempest.conf.j2
@@ -74,7 +74,8 @@ image_ref = {{ tempest_glance_image_id_1 }}
 image_ref_alt = {{ tempest_glance_image_id_2 }}
 flavor_ref = {{ tempest_nova_flavor_id_1 }}
 flavor_ref_alt = {{ tempest_nova_flavor_id_2 }}
-{% if not tempest_create_isolated_networks | bool %}
+# do not define fixed_network_name when dynamic credentials are used together with tempest_create_isolated_networks
+{% if not ((tempest_test_accounts | length == 0) and (tempest_create_isolated_networks | bool)) %}
 fixed_network_name = {{ tempest_fixed_network_name }}
 {% endif %}
 endpoint_type = {{ tempest_endpoint_type }}