diff --git a/html_to_text.inc b/html_to_text.inc
index 0857622..e02a28c 100644
--- a/html_to_text.inc
+++ b/html_to_text.inc
@@ -134,6 +134,9 @@ function mailsystem_html_to_text($string, $allowed_tags = NULL) {
       $text .= $eol . '[' . $note . '] ' . $url;
     }
   }
+  if (empty(trim($text)) && !empty(trim($string)) {
+    watchdog('mailsystem', 'Converting "@html" to text yields an empty string.', array('@html' => $string), WATCHDOG_WARNING);
+  }
   return $text;
 }