diff --git a/sshdpw b/sshdpw
index 599cc6b..bd87259 100755
--- a/sshdpw
+++ b/sshdpw
@@ -15,6 +15,14 @@ case "${1}" in
     else
       FROM=no; TO=yes;
     fi
+    ;;
+  *)
+    echo 'Must specify one of the following:'
+    echo '  [ on | yes | enable | unlock ] to allow interactive passwords'
+    echo '  [ off | no | disable | lock ] to disallow interactive passwords'
+    echo '  [ toggle ] to toggle the allowance of interactive passwords'
+    echo '  [ status ] to show the current state of interactive passwords'
+    exit 1
   ;;
 esac