diff --git a/tests/test_calcat_interface2.py b/tests/test_calcat_interface2.py
index 8bdf3a2ac703f3f95fd6027ca7adb10d48b4fee8..5b3e82b3a7f38792de97130530c71a22e12b1298 100644
--- a/tests/test_calcat_interface2.py
+++ b/tests/test_calcat_interface2.py
@@ -67,7 +67,7 @@ def test_DSSC_modules_missing():
     )
     # DSSC was used with only 3 quadrants at this point
     modnos = list(range(4)) + list(range(8, 16))
-    assert dssc_cd.aggregator_names == ['DSSC{m:02}' for m in modnos]
+    assert dssc_cd.aggregator_names == [f'DSSC{m:02}' for m in modnos]
     assert dssc_cd.module_nums == modnos
     assert dssc_cd.qm_names == [
         f"Q{(m // 4) + 1}M{(m % 4) + 1}" for m in modnos