diff --git a/eessi/testsuite/utils.py b/eessi/testsuite/utils.py
index 5fde4b4b..c68a7ec8 100644
--- a/eessi/testsuite/utils.py
+++ b/eessi/testsuite/utils.py
@@ -117,9 +117,9 @@ def find_modules(regex: str, name_only=True) -> Iterator[str]:
                 seen.add(orig_mod)
             yield orig_mod
 
-    if dupes != []:
-        err_msg = "EESSI test-suite cannot handle duplicate modules."
-        err_msg += "Please make sure that only one is available on your system."
+    if dupes:
+        err_msg = "EESSI test-suite cannot handle duplicate modules. "
+        err_msg += "Please make sure that only one is available on your system. "
         err_msg += f"The following modules have a duplicate on your system: {dupes}"
         raise ValueError(err_msg)