diff --git a/README.md b/README.md
index 93251f2..540255f 100644
--- a/README.md
+++ b/README.md
@@ -36,7 +36,7 @@ Examples of the four combinations:
 Options can be abbreviated per Getopt::Long
 
 <dl>
-  <dt> `--api-url`:</dt> <dd>Base URL of the wiki</dd>
+  <dt> `--api-url`:</dt> <dd>Base URL of the wiki. Required.</dd>
 </dl>
 Template names. Defaults to MapRegion, MapSubregion, MapLocation, MapSite.
 <dl>