diff --git a/README.rst b/README.rst
index 6df741a..a63cbd0 100644
--- a/README.rst
+++ b/README.rst
@@ -75,6 +75,9 @@ the known modules using a nicer syntax::
   [tool.flake8.known-modules]
   my-lib = ["mylib.drm", "mylib.encryption"]
 
+Note that if the module's name contains dots, you have to quote it in pyproject.toml (e.g.
+``"my_namespace.my_lib" = [...]``).
+
 It is also possible to scan host's site-packages directory for installed packages. This feature is
 disabled by default, but user can enable it with the ``--scan-host-site-packages`` command line
 option. Please note, however, that the location of the site-packages directory will be determined
diff --git a/setup.cfg b/setup.cfg
index 354bc3d..e096a8c 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,5 +1,8 @@
 [bdist_wheel]
 universal = 1
 
+[doc8]
+max-line-length = 99
+
 [isort]
 force_single_line = true