diff --git a/logging/monolog_regex_based_excludes.rst b/logging/monolog_regex_based_excludes.rst
index d382dbc74dc..bc383dbff30 100644
--- a/logging/monolog_regex_based_excludes.rst
+++ b/logging/monolog_regex_based_excludes.rst
@@ -60,3 +60,12 @@ configuration:
                 ],
             ],
         ]);
+
+
+.. caution::
+    Combining ``excluded_404s`` with a ``passthru_level`` lower than
+    ``error`` (i.e. ``debug``, ``info``, ``notice`` or ``warning``) will not
+    actually exclude log messages for the URL(s) listed in ``excluded_404s``
+    because they are logged with level of ``error`` or higher and
+    ``passthru_level`` takes precedence over the URLs being listed in
+    ``excluded_404s``.