diff --git a/setup.cfg b/setup.cfg
index 42291e82433c3c7522f8e267e41321c4d19db099..ed2c99f4b846865ae1cf244a2fa99f99e2ad061d 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -5,3 +5,5 @@ exclude=
     pytential/symbolic/old_diffop_primitives.py,
     pytential/symbolic/pde/maxwell/generalized_debye.py,
 
+[tool:pytest]
+python_classes=