diff --git a/prometheus_client/multiprocess.py b/prometheus_client/multiprocess.py
index db55874e..046bb2c2 100644
--- a/prometheus_client/multiprocess.py
+++ b/prometheus_client/multiprocess.py
@@ -178,6 +178,8 @@ def mark_process_dead(pid, path=None):
     """Do bookkeeping for when one process dies in a multi-process setup."""
     if path is None:
         path = os.environ.get('PROMETHEUS_MULTIPROC_DIR', os.environ.get('prometheus_multiproc_dir'))
+    if not path:
+        return
     for mode in _LIVE_GAUGE_MULTIPROCESS_MODES:
         for f in glob.glob(os.path.join(path, f'gauge_{mode}_{pid}.db')):
             os.remove(f)
diff --git a/tests/test_multiprocess.py b/tests/test_multiprocess.py
index eab93f50..2b68e67b 100644
--- a/tests/test_multiprocess.py
+++ b/tests/test_multiprocess.py
@@ -51,6 +51,11 @@ def test_mark_process_dead_respects_lowercase(self):
         # logic is tested elsewhere.
         mark_process_dead(123)
 
+    def test_mark_process_dead_noop_when_path_unset(self):
+        os.environ.pop('prometheus_multiproc_dir', None)
+        os.environ.pop('PROMETHEUS_MULTIPROC_DIR', None)
+        mark_process_dead(123)
+
 
 class TestMultiProcess(unittest.TestCase):
     def setUp(self):