diff --git a/src/cal_tools/tools.py b/src/cal_tools/tools.py
index 774424a444d76b0522c106ec8c417441266ca1a5..18092b32c0676766d8d82e9b9a3d69412eb4a4c6 100644
--- a/src/cal_tools/tools.py
+++ b/src/cal_tools/tools.py
@@ -127,10 +127,14 @@ def map_modules_from_folder(
     sequences_qm = {}
     for inset in karabo_da:
         module_idx = int(inset[-2:])
+
         if key_name == "qm":
             name = module_index_to_qm(module_idx)
-        else:
+        elif key_name == "da":
             name = inset  # karabo_da
+        else:
+            raise ValueError("key_name must be 'da' or 'qm'")
+
         module_files[name] = Queue()
         sequences_qm[name] = 0
         mod_ids[name] = module_idx