diff --git a/pyproject.toml b/pyproject.toml
index c67379a9..4821c013 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -168,6 +168,7 @@ norecursedirs = [".git"]
 addopts = [
   "-svx",
   "-ra",
+  "-W error",
   "--strict-config",
   "--strict-markers",
   "--doctest-modules",