diff --git a/README.rst b/README.rst
index 0c17bd4..1b83af2 100644
--- a/README.rst
+++ b/README.rst
@@ -109,6 +109,9 @@ usage examples.
                           Username to use with basic HTTP authentication
       -p PASSWORD, --password=PASSWORD
                           Password to use with basic HTTP authentication
+      -D HEADER, --header=HEADER
+                          custom header of the form Header: Value (repeat for
+                          multiple headers)
       -t TYPES, --types=TYPES
                           Comma-separated values of tags to look for when
                           crawling a site. Default (and supported types):
diff --git a/pylinkvalidator/models.py b/pylinkvalidator/models.py
index 7311ea7..54e33a9 100644
--- a/pylinkvalidator/models.py
+++ b/pylinkvalidator/models.py
@@ -289,7 +289,7 @@ def _build_parser(self):
             help="password to use with basic HTTP authentication")
         crawler_group.add_option(
             "-D", "--header",
-            dest="headers",  action="append",
+            dest="headers",  action="append", metavar="HEADER",
             help="custom header of the form Header: Value "
             "(repeat for multiple headers)")
         # crawler_group.add_option("-U", "--unique", dest="unique",