diff --git a/ansible_mitogen/runner.py b/ansible_mitogen/runner.py
index 86f7b329..1cc02198 100644
--- a/ansible_mitogen/runner.py
+++ b/ansible_mitogen/runner.py
@@ -44,6 +44,7 @@ import imp
 import json
 import logging
 import os
+import shlex
 import sys
 import tempfile
 import types
@@ -78,6 +79,22 @@ for symbol in 'res_init', '__res_init':
     except AttributeError:
         pass
 
+# For tasks running on Linux machines, with vanilla Ansible, edits to
+# /etc/environment and ~/.pam_environment are reflected if become:true, due to
+# sudo reinvoking pam_env. If multiplexing is disabled, then edits are also
+# reflected with become:false. Rather than emulate existing semantics, simply
+# always ensure edits are reflects for the next task.
+try:
+    etc_env_st = os.stat('/etc/environment')
+except OSError:
+    etc_env_st = None
+
+try:
+    pam_env_st = os.stat(os.path.expanduser('~/.pam_environment'))
+except OSError:
+    pam_env_st = None
+
+
 iteritems = getattr(dict, 'iteritems', dict.items)
 LOG = logging.getLogger(__name__)
 
@@ -104,6 +121,54 @@ def reopen_readonly(fp):
     os.close(fd)
 
 
+def parse_env(fp):
+    """
+    Parse /etc/environ using roughly the same syntax as pam_env.
+    """
+    # https://github.com/linux-pam/linux-pam/blob/v1.3.1/modules/pam_env/pam_env.c#L207
+    for line in fp:
+        # '   #export foo=some var  ' -> ['#export', 'foo=some var  ']
+        bits = shlex.split(line, comments=True)
+        if not bits:
+            continue
+
+        if bits[0] == 'export':
+            bits.pop(0)
+
+        key, sep, value = (' '.join(bits)).partition('=')
+        if sep:
+            os.environ[key] = value
+
+
+def reload_env(old_st, path):
+    """
+    Compare the :func:`os.stat` for the pam_env style environmnt file `path`
+    with the previous result `old_st`, which may be :data:`None` if the
+    previous stat attempt failed. Reload its contents if the file has changed
+    or appeared since last attempt.
+
+    :returns:
+        New :func:`os.stat` result. The new call to :func:`reload_env` should
+        pass it as the value of `old_st`.
+    """
+    try:
+        path = os.path.expanduser(path)
+        st = os.stat(path)
+    except OSError:
+        return None
+
+    if old_st == st:
+        return old_st
+    if st is None:
+        LOG.debug('reload_env(%r): file has disappeared', path)
+        return st
+
+    LOG.debug('reload_env(%r): file has changed or appeared, reloading', path)
+    with open(path) as fp:
+        parse_env(fp)
+    return st
+
+
 class Runner(object):
     """
     Ansible module runner. After instantiation (with kwargs supplied by the
@@ -163,8 +228,22 @@ class Runner(object):
         env = dict(self.extra_env or {})
         if self.env:
             env.update(self.env)
+        self._setup_environ()
         self._env = TemporaryEnvironment(env)
 
+    def _setup_environ(self):
+        """
+        Ensure /etc/environment and ~/.pam_environment are reloaded if their
+        content appears to differ since execution of the previous task. This
+        must happen before TemporaryEnvironment is installed, to ensure changes
+        persist across tasks.
+        """
+        global etc_env_st
+        etc_env_st = reload_env(etc_env_st, '/etc/environment')
+
+        global pam_env_st
+        pam_env_st = reload_env(pam_env_st, '~/.pam_environment')
+
     def revert(self):
         """
         Revert any changes made to the process after running a module. The base
diff --git a/tests/ansible/integration/runner/all.yml b/tests/ansible/integration/runner/all.yml
index 5242a405..8f4f3426 100644
--- a/tests/ansible/integration/runner/all.yml
+++ b/tests/ansible/integration/runner/all.yml
@@ -1,7 +1,7 @@
 - import_playbook: builtin_command_module.yml
+- import_playbook: custom_bash_hashbang_argument.yml
 - import_playbook: custom_bash_old_style_module.yml
 - import_playbook: custom_bash_want_json_module.yml
-- import_playbook: custom_bash_hashbang_argument.yml
 - import_playbook: custom_binary_producing_json.yml
 - import_playbook: custom_binary_producing_junk.yml
 - import_playbook: custom_binary_single_null.yml
@@ -13,4 +13,5 @@
 - import_playbook: custom_python_want_json_module.yml
 - import_playbook: custom_script_interpreter.yml
 - import_playbook: environment_isolation.yml
+- import_playbook: etc_environment.yml
 - import_playbook: forking_behaviour.yml
diff --git a/tests/ansible/integration/runner/etc_environment.yml b/tests/ansible/integration/runner/etc_environment.yml
new file mode 100644
index 00000000..4c7f64d8
--- /dev/null
+++ b/tests/ansible/integration/runner/etc_environment.yml
@@ -0,0 +1,66 @@
+# issue #338: ensure /etc/environment is reloaded if it changes.
+# Actually this test uses ~/.pam_environment, which is using the same logic,
+# but less likely to brick a development workstation
+
+- name: integration/runner/etc_environment.yml
+  hosts: test-targets
+  any_errors_fatal: true
+  gather_facts: true
+  tasks:
+    - meta: end_play
+      when: ansible_virtualization_type != "docker"
+
+
+    # ~/.pam_environment
+
+    - file:
+        path: ~/.pam_environment
+        state: absent
+
+    - shell: echo $MAGIC_NEW_ENV
+      register: echo
+
+    - assert:
+        that: echo.stdout == ""
+
+    - copy:
+        dest: ~/.pam_environment
+        content: |
+          MAGIC_NEW_ENV=321
+
+    - shell: echo $MAGIC_NEW_ENV
+      register: echo
+
+    - assert:
+        that: echo.stdout == "321"
+
+    - file:
+        path: ~/.pam_environment
+        state: absent
+
+    # /etc/environment
+
+    - file:
+        path: /etc/environment
+        state: absent
+
+    - shell: echo $MAGIC_ETC_ENV
+      register: echo
+
+    - assert:
+        that: echo.stdout == ""
+
+    - copy:
+        dest: /etc/environment
+        content: |
+          MAGIC_ETC_ENV=555
+
+    - shell: echo $MAGIC_ENV_ENV
+      register: echo
+
+    - assert:
+        that: echo.stdout == "555"
+
+    - file:
+        path: /etc/environment
+        state: absent