diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index e728bffb..c1e64630 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -10,12 +10,14 @@
 
     ```toml
     [tool.pytest.ini_options]
-    addopts = "-W=all -vv"
+    addopts = "-W=all -Werror -Wdefault::DeprecationWarning -Wdefault::PendingDeprecationWarning -vv"
     ```
 
 ### Cookiecutter template
 
-All upgrading should be done via the migration script or regenerating the templates.
+All upgrading should be done via the migration script or regenerating the templates. But you might still need to adapt your code:
+
+- `pytest` now uses `-Werror` by default (but still treat deprecations as normal warnings), so if your tests run with warnings, they will now be turned to errors, and you'll need to fix them.
 
 ## New Features
 
@@ -23,7 +25,7 @@ All upgrading should be done via the migration script or regenerating the templa
 
 ### Cookiecutter template
 
-<!-- Here new features for cookiecutter specifically -->
+- `pytest` now uses `-Werror -Wdefault::DeprecationWarning -Wdefault::PendingDeprecationWarning` by default. Deprecations are still treated as warnings, as when testing with the `pytest_min` session is normal to get deprecation warnings as we are using old versions of dependencies.
 
 ## Bug Fixes
 
diff --git a/cookiecutter/migrate.py b/cookiecutter/migrate.py
index dfb9e4b4..7e57f4b8 100644
--- a/cookiecutter/migrate.py
+++ b/cookiecutter/migrate.py
@@ -40,7 +40,7 @@ def add_default_pytest_options() -> None:
     pyproject_toml = Path("pyproject.toml")
     pyproject_toml_content = pyproject_toml.read_text(encoding="utf-8")
     marker = "[tool.pytest.ini_options]\n"
-    new_options = "-W=all -vv"
+    new_options = "-W=all Werror -Wdefault::DeprecationWarning -Wdefault::PendingDeprecationWarning -vv"
 
     print(f"Adding default pytest options to {pyproject_toml}...")
     if pyproject_toml_content.find(marker) == -1:
diff --git a/cookiecutter/{{cookiecutter.github_repo_name}}/pyproject.toml b/cookiecutter/{{cookiecutter.github_repo_name}}/pyproject.toml
index 40bf6964..ef45b2ec 100644
--- a/cookiecutter/{{cookiecutter.github_repo_name}}/pyproject.toml
+++ b/cookiecutter/{{cookiecutter.github_repo_name}}/pyproject.toml
@@ -203,7 +203,7 @@ disable = [
 
 [tool.pytest.ini_options]
 {%- if cookiecutter.type != "api" %}
-addopts = "-W=all -vv"
+addopts = "-W=all -Werror -Wdefault::DeprecationWarning -Wdefault::PendingDeprecationWarning -vv"
 testpaths = ["tests", "src"]
 asyncio_mode = "auto"
 asyncio_default_fixture_loop_scope = "function"
diff --git a/pyproject.toml b/pyproject.toml
index e7b7cc49..e923f004 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -205,7 +205,7 @@ module = [
 ignore_missing_imports = true
 
 [tool.pytest.ini_options]
-addopts = "-W=all -vv"
+addopts = "-W=all -Werror -Wdefault::DeprecationWarning -Wdefault::PendingDeprecationWarning -vv"
 testpaths = ["src", "tests"]
 markers = [
   "integration: integration tests (deselect with '-m \"not integration\"')",
diff --git a/tests_golden/integration/test_cookiecutter_generation/actor/frequenz-actor-test/pyproject.toml b/tests_golden/integration/test_cookiecutter_generation/actor/frequenz-actor-test/pyproject.toml
index 860c1956..a8985a80 100644
--- a/tests_golden/integration/test_cookiecutter_generation/actor/frequenz-actor-test/pyproject.toml
+++ b/tests_golden/integration/test_cookiecutter_generation/actor/frequenz-actor-test/pyproject.toml
@@ -153,7 +153,7 @@ disable = [
 ]
 
 [tool.pytest.ini_options]
-addopts = "-W=all -vv"
+addopts = "-W=all -Werror -vv"
 testpaths = ["tests", "src"]
 asyncio_mode = "auto"
 asyncio_default_fixture_loop_scope = "function"
diff --git a/tests_golden/integration/test_cookiecutter_generation/app/frequenz-app-test/pyproject.toml b/tests_golden/integration/test_cookiecutter_generation/app/frequenz-app-test/pyproject.toml
index aa080686..0ee9a7cb 100644
--- a/tests_golden/integration/test_cookiecutter_generation/app/frequenz-app-test/pyproject.toml
+++ b/tests_golden/integration/test_cookiecutter_generation/app/frequenz-app-test/pyproject.toml
@@ -152,7 +152,7 @@ disable = [
 ]
 
 [tool.pytest.ini_options]
-addopts = "-W=all -vv"
+addopts = "-W=all -Werror -vv"
 testpaths = ["tests", "src"]
 asyncio_mode = "auto"
 asyncio_default_fixture_loop_scope = "function"
diff --git a/tests_golden/integration/test_cookiecutter_generation/lib/frequenz-test-python/pyproject.toml b/tests_golden/integration/test_cookiecutter_generation/lib/frequenz-test-python/pyproject.toml
index 723a3b6c..4c2134f3 100644
--- a/tests_golden/integration/test_cookiecutter_generation/lib/frequenz-test-python/pyproject.toml
+++ b/tests_golden/integration/test_cookiecutter_generation/lib/frequenz-test-python/pyproject.toml
@@ -149,7 +149,7 @@ disable = [
 ]
 
 [tool.pytest.ini_options]
-addopts = "-W=all -vv"
+addopts = "-W=all -Werror -vv"
 testpaths = ["tests", "src"]
 asyncio_mode = "auto"
 asyncio_default_fixture_loop_scope = "function"
diff --git a/tests_golden/integration/test_cookiecutter_generation/model/frequenz-model-test/pyproject.toml b/tests_golden/integration/test_cookiecutter_generation/model/frequenz-model-test/pyproject.toml
index 3e662c9d..a1fcc2bf 100644
--- a/tests_golden/integration/test_cookiecutter_generation/model/frequenz-model-test/pyproject.toml
+++ b/tests_golden/integration/test_cookiecutter_generation/model/frequenz-model-test/pyproject.toml
@@ -153,7 +153,7 @@ disable = [
 ]
 
 [tool.pytest.ini_options]
-addopts = "-W=all -vv"
+addopts = "-W=all -Werror -vv"
 testpaths = ["tests", "src"]
 asyncio_mode = "auto"
 asyncio_default_fixture_loop_scope = "function"