diff --git a/tests/test_modelchain.py b/tests/test_modelchain.py
index ecc2c41447..a3abece9d8 100644
--- a/tests/test_modelchain.py
+++ b/tests/test_modelchain.py
@@ -139,7 +139,8 @@ def cec_dc_adr_ac_system(sam_data, cec_module_cs5p_220m,
                       module=module_parameters['Name'],
                       module_parameters=module_parameters,
                       temperature_model_parameters=temp_model_params,
-                      inverter_parameters=inverter)
+                      inverter_parameters=inverter,
+                      modules_per_string=14)
     return system