diff --git a/docs/settings.rst b/docs/settings.rst
index cc67815b..fbd6169c 100644
--- a/docs/settings.rst
+++ b/docs/settings.rst
@@ -13,7 +13,7 @@ You can also specify extra settings via ``-e`` / ``--extra-settings`` option
 flags, which will override default settings as well as any defined within
 settings files::
 
-    pelican content -e DELETE_OUTPUT_DIRECTORY=True
+    pelican content -e DELETE_OUTPUT_DIRECTORY=true
 
 .. note::
 
diff --git a/pelican/settings.py b/pelican/settings.py
index 40804e0b..1554c1f1 100644
--- a/pelican/settings.py
+++ b/pelican/settings.py
@@ -662,10 +662,12 @@ def configure_settings(settings):
 
 
 def coerce_overrides(overrides):
+    if overrides is None:
+        return {}
     coerced = {}
     types_to_cast = {int, str}
     for k, v in overrides.items():
-        if k not in overrides:
+        if k not in DEFAULT_CONFIG:
             logger.warning('Override for unknown setting %s, ignoring', k)
             continue
         setting_type = type(DEFAULT_CONFIG[k])