diff --git a/docs/changelog.rst b/docs/changelog.rst
index ce84593c..2f31dfd8 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -21,6 +21,7 @@ To avail of fixes in an unreleased version, please download a ZIP file
 In progress (unreleased)
 ------------------------
 
+* :gh:issue:`1213` tests: Enable default Python warnings
 
 
 v0.3.21 (2025-01-20)
diff --git a/tox.ini b/tox.ini
index 779d1e1a..bd2d65e9 100644
--- a/tox.ini
+++ b/tox.ini
@@ -105,6 +105,8 @@ setenv =
     NOCOVERAGE_ERASE = 1
     NOCOVERAGE_REPORT = 1
     PIP_CONSTRAINT={toxinidir}/tests/constraints.txt
+    # Print warning on the first occurence at each module:linenno in Mitogen. Available Python 2.7, 3.2+.
+    PYTHONWARNINGS=default:::ansible_mitogen,default:::mitogen
     # Ansible 6 - 8 (ansible-core 2.13 - 2.15) require Python 2.7 or >= 3.5 on targets
     ansible6: MITOGEN_TEST_DISTRO_SPECS=centos7 centos8 debian9 debian10 debian11 ubuntu1604 ubuntu1804 ubuntu2004
     ansible7: MITOGEN_TEST_DISTRO_SPECS=centos7 centos8 debian9 debian10 debian11 ubuntu1604 ubuntu1804 ubuntu2004