diff --git a/setup.cfg b/setup.cfg
index ccb7e01..d9a9c10 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -64,6 +64,7 @@ addopts =
 addopts =
     --cov wafo --cov-report term-missing
     --verbose
+    --doctest-modules
 
 [aliases]
 docs = build_sphinx