diff --git a/tests/test_separator.py b/tests/test_separator.py
index c570e64..d2648c2 100644
--- a/tests/test_separator.py
+++ b/tests/test_separator.py
@@ -54,7 +54,7 @@ def test_separate_to_file(configuration, instruments):
         for instrument in instruments:
             assert exists(join(directory, '{}.wav'.format(instrument)))
         for instrument in instruments:
-            for compared in instrument:
+            for compared in instruments:
                 if instrument != compared:
                     assert not filecmp.cmp(
                         join(directory, '{}.wav'.format(instrument)),