diff --git a/config/vsc_hortense.py b/config/vsc_hortense.py
index 2036f5e4..4078026d 100644
--- a/config/vsc_hortense.py
+++ b/config/vsc_hortense.py
@@ -118,7 +118,7 @@ def command(self, job):
                     'descr': 'CPU nodes (AMD Milan, 256GiB RAM)',
                     'max_jobs': 20,
                     'launcher': launcher,
-                    'modules': [mpi_module % 'cpu_milan'],
+                    'modules': [mpi_module.format('cpu_milan')],
                     'resources': [
                         {
                             'name': 'memory',