diff --git a/linkchecker b/linkchecker
index 0dbb8f28..7f234835 100755
--- a/linkchecker
+++ b/linkchecker
@@ -621,6 +621,13 @@ if constructauth:
 
 linkcheck.log.debug(linkcheck.LOG_CMDLINE, "configuration: %s",
                     pprint.pformat(config.items()))
+# warn about sitemap loggers and verbose output
+klasses = [c.__class__ for c in [config['logger']] + config['fileoutput']]
+if (linkcheck.logger.gml.GMLLogger in klasses or \
+    linkcheck.logger.dot.DOTLogger in klasses) and not config['verbose']:
+    linkcheck.log.warn(linkcheck.LOG_CMDLINE,
+           _("Using DOT or GML loggers without verbose output"
+             " gives an incomplete sitemap graph."))
 
 # try to generate empty config dir if not already there
 userconfdir = linkcheck.configuration.normpath("~/.linkchecker")