diff --git a/ansible_mitogen/mixins.py b/ansible_mitogen/mixins.py
index 18518d69..8ddbb437 100644
--- a/ansible_mitogen/mixins.py
+++ b/ansible_mitogen/mixins.py
@@ -29,6 +29,7 @@
 from __future__ import absolute_import, division, print_function
 __metaclass__ = type
 
+import json
 import logging
 import os
 import pwd
@@ -42,7 +43,6 @@ import ansible.vars.clean
 
 from ansible.module_utils.common.text.converters import to_bytes, to_text
 from ansible.module_utils.six.moves import shlex_quote
-from ansible.parsing.utils.jsonify import jsonify
 
 import mitogen.core
 import mitogen.select
@@ -219,8 +219,13 @@ class ActionModuleMixin(ansible.plugins.action.ActionBase):
         Used by the base _execute_module(), and in <2.4 also by the template
         action module, and probably others.
         """
+        if data is None and ansible_mitogen.utils.ansible_version[:2] <= (2, 18):
+            data = '{}'
         if isinstance(data, dict):
-            data = jsonify(data)
+            try:
+                data = json.dumps(data, ensure_ascii=False)
+            except UnicodeDecodeError:
+                data = json.dumps(data)
         if not isinstance(data, bytes):
             data = to_bytes(data, errors='surrogate_or_strict')
 
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 5b2ec785..f0327e0f 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -32,6 +32,8 @@ Running Ansible 12 + Mitogen will currently print a deprecation warning
 Ansible + Mitogen will still work for now. Mitogen is considering alternatives
 to strategy plugins under :gh:issue:`1278`.
 
+* :gh:issue:`1274` :mod:`ansible_mitogen`: Replace use of `jsonify()`, which
+  is deprecated form Ansible 12 (ansible-core 2.19)
 
 v0.3.25a1 (2025-06-05)
 ----------------------