diff --git a/fasteners/process_lock.py b/fasteners/process_lock.py
index c540f86..f35b83b 100644
--- a/fasteners/process_lock.py
+++ b/fasteners/process_lock.py
@@ -41,6 +41,8 @@ def _ensure_tree(path):
                 raise
             else:
                 return False
+        elif e.errno == errno.EISDIR:
+            return False
         else:
             raise
     else: