diff --git a/.ci/ansible_tests.py b/.ci/ansible_tests.py
index 4a7bedaeb..785b75604 100755
--- a/.ci/ansible_tests.py
+++ b/.ci/ansible_tests.py
@@ -79,7 +79,7 @@ def pause_if_interactive():
 with ci_lib.Fold('ansible'):
     playbook = os.environ.get('PLAYBOOK', 'all.yml')
     try:
-        ci_lib.run('./run_ansible_playbook.py %s -i "%s" %s',
+        ci_lib.run('python -b ./run_ansible_playbook.py %s -i "%s" %s',
             playbook, HOSTS_DIR, ' '.join(sys.argv[1:]))
     except:
         pause_if_interactive()
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 9a275a00c..75c05df94 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -157,7 +157,7 @@ jobs:
               exit 1
           fi
 
-          "$PYTHON" -m tox -e "${{ matrix.tox_env }}"
+          "$PYTHON" -b -m tox -e "${{ matrix.tox_env }}"
 
   macos:
     # https://github.com/actions/runner-images/blob/main/images/macos/macos-13-Readme.md
@@ -255,7 +255,7 @@ jobs:
               PYTHON="/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7"
           fi
 
-          "$PYTHON" -m tox -e "${{ matrix.tox_env }}"
+          "$PYTHON" -b -m tox -e "${{ matrix.tox_env }}"
 
   # https://github.com/marketplace/actions/alls-green
   check:
diff --git a/ansible_mitogen/target.py b/ansible_mitogen/target.py
index ee4cb398f..4318b234f 100644
--- a/ansible_mitogen/target.py
+++ b/ansible_mitogen/target.py
@@ -52,6 +52,7 @@
 import traceback
 import types
 
+import mitogen
 import mitogen.core
 import mitogen.parent
 import mitogen.service
diff --git a/mitogen/master.py b/mitogen/master.py
index 927ccaf11..b1ab68f7f 100644
--- a/mitogen/master.py
+++ b/mitogen/master.py
@@ -169,8 +169,8 @@ def is_stdlib_path(path):
 
 def get_child_modules(path, fullname):
     """
-    Return the suffixes of submodules directly neated beneath of the package
-    directory at `path`.
+    Return the suffixes for any direct submodules in package named fullname,
+    located at path.
 
     :param str path:
         Path to the module's source code on disk, or some PEP-302-recognized
@@ -1051,6 +1051,7 @@ def find_related_imports(self, fullname):
                 if sys.modules.get(name) is not None
                 and not is_stdlib_name(name)
                 and u'six.moves' not in name  # TODO: crap
+                and name != u'__main__'
             )
         ))
 
diff --git a/mitogen/parent.py b/mitogen/parent.py
index f301a42c5..4e7a48cd8 100644
--- a/mitogen/parent.py
+++ b/mitogen/parent.py
@@ -1470,7 +1470,7 @@ def get_boot_command(self):
         # `import os` here, instead of stage 1, to save a few bytes.
         # `sys.path=...` for https://github.com/python/cpython/issues/115911.
         return self.get_python_argv() + [
-            '-c',
+            '-b', '-c',
             'import sys;sys.path=[p for p in sys.path if p];import binascii,os,zlib;'
             'exec(zlib.decompress(binascii.a2b_base64("%s")))' % (encoded.decode(),),
         ]
diff --git a/run_tests b/run_tests
index 75663d15c..9b66e183f 100755
--- a/run_tests
+++ b/run_tests
@@ -40,7 +40,7 @@ fi
             --pattern '*_test.py' \
             "$@"
     else
-        python -m unittest discover \
+        python -b -m unittest discover \
             --start-directory "tests" \
             --pattern '*_test.py' \
             "$@"
@@ -61,7 +61,7 @@ fi
             --pattern '*_test.py' \
             "$@"
     else
-        python -m unittest discover \
+        python -b -m unittest discover \
             --start-directory "tests/ansible" \
             --pattern '*_test.py' \
             "$@"
diff --git a/tests/ansible/run_ansible_playbook.py b/tests/ansible/run_ansible_playbook.py
index 04c0c9db1..63804425a 100755
--- a/tests/ansible/run_ansible_playbook.py
+++ b/tests/ansible/run_ansible_playbook.py
@@ -43,7 +43,8 @@
 if 'ANSIBLE_ARGV' in os.environ:
     args = eval(os.environ['ANSIBLE_ARGV'])
 else:
-    args = ['ansible-playbook']
+    bin_dir = os.path.dirname(sys.executable)
+    args = ['python', '-b', os.path.join(bin_dir, 'ansible-playbook')]
 
 args += ['-e', json.dumps(extra)]
 args += sys.argv[1:]
diff --git a/tests/jail_test.py b/tests/jail_test.py
index 5c0ad9469..732dbe8fe 100644
--- a/tests/jail_test.py
+++ b/tests/jail_test.py
@@ -14,10 +14,7 @@ def test_okay(self):
         stream = self.router.stream_by_id(context.context_id)
 
         argv = eval(context.call(os.getenv, 'ORIGINAL_ARGV'))
-        self.assertEqual(argv[:4], [
-            self.jexec_path,
-            'somejail',
-            stream.conn.options.python_path,
-            '-c',
-        ])
+
+        self.assertEqual(argv[:3], [self.jexec_path, 'somejail', stream.conn.options.python_path])
+        self.assertEqual(argv[-2], '-c')
         self.assertEqual('1', context.call(os.getenv, 'THIS_IS_STUB_JEXEC'))
diff --git a/tox.ini b/tox.ini
index bd2d65e98..26c17e98b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -91,10 +91,10 @@ install_command =
 commands_pre =
     mode_debops_common: {toxinidir}/.ci/debops_common_install.py
 commands =
-    mode_ansible: {toxinidir}/.ci/ansible_tests.py
+    mode_ansible: python -b {toxinidir}/.ci/ansible_tests.py
     mode_debops_common: {toxinidir}/.ci/debops_common_tests.py
-    mode_localhost: {toxinidir}/.ci/localhost_ansible_tests.py
-    mode_mitogen: {toxinidir}/.ci/mitogen_tests.py
+    mode_localhost: python -b {toxinidir}/.ci/localhost_ansible_tests.py
+    mode_mitogen: python -b {toxinidir}/.ci/mitogen_tests.py
 passenv =
     ANSIBLE_*
     HOME
@@ -106,7 +106,7 @@ setenv =
     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
+    PYTHONWARNINGS=default:::ansible,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