diff --git a/ansible_mitogen/planner.py b/ansible_mitogen/planner.py
index 801950f9..4c3ef876 100644
--- a/ansible_mitogen/planner.py
+++ b/ansible_mitogen/planner.py
@@ -290,15 +290,26 @@ class NewStylePlanner(ScriptPlanner):
     def get_module_deps(self):
         return self.get_module_map()['builtin']
 
+    #: Module names appearing in this set always require forking, usually due
+    #: to some terminal leakage that cannot be worked around in any sane
+    #: manner.
+    ALWAYS_FORK_MODULES = frozenset([
+        'dnf',  # issue #280; py-dnf/hawkey need therapy
+    ])
+
     def should_fork(self):
         """
         In addition to asynchronous tasks, new-style modules should be forked
-        if the user specifies mitogen_task_isolation=fork, or if the new-style
-        module has a custom module search path.
+        if:
+
+        * the user specifies mitogen_task_isolation=fork, or
+        * the new-style module has a custom module search path, or
+        * the module is known to leak like a sieve.
         """
         return (
             super(NewStylePlanner, self).should_fork() or
             (self._inv.task_vars.get('mitogen_task_isolation') == 'fork') or
+            (self._inv.module_name in self.ALWAYS_FORK_MODULES) or
             (len(self.get_module_map()['custom']) > 0)
         )
 
diff --git a/mitogen/core.py b/mitogen/core.py
index ebd41f84..bfe33dec 100644
--- a/mitogen/core.py
+++ b/mitogen/core.py
@@ -623,7 +623,7 @@ class Importer(object):
         fullname = fullname.rstrip('.')
         try:
             pkgname, dot, _ = fullname.rpartition('.')
-            _v and LOG.debug('%r.find_module(%r)', self, fullname)
+            _vv and IOLOG.debug('%r.find_module(%r)', self, fullname)
             suffix = fullname[len(pkgname+dot):]
             if suffix not in self._present.get(pkgname, (suffix,)):
                 _v and LOG.debug('%r: master doesn\'t know %r', self, fullname)
@@ -631,8 +631,10 @@ class Importer(object):
 
             pkg = sys.modules.get(pkgname)
             if pkg and getattr(pkg, '__loader__', None) is not self:
-                _v and LOG.debug('%r: %r is submodule of a package we did not load',
-                          self, fullname)
+                _vv and IOLOG.debug(
+                    '%r: %r is submodule of a package we did not load',
+                    self, fullname
+                )
                 return None
 
             # #114: explicitly whitelisted prefixes override any
@@ -643,9 +645,10 @@ class Importer(object):
 
             try:
                 self.builtin_find_module(fullname)
-                _v and LOG.debug('%r: %r is available locally', self, fullname)
+                _vv and IOLOG.debug('%r: %r is available locally',
+                                    self, fullname)
             except ImportError:
-                _v and LOG.debug('find_module(%r) returning self', fullname)
+                _vv and IOLOG.debug('find_module(%r) returning self', fullname)
                 return self
         finally:
             del _tls.running