diff --git a/web/app.html b/web/app.html
index 6582290..1ddbe9b 100644
--- a/web/app.html
+++ b/web/app.html
@@ -23,7 +23,7 @@
     <div class="btn-toolbar btn-group-sm" role="toolbar" aria-label="Toolbar">
       <div class="btn-group mr-2 w-50" role="group" aria-label="Add group">
         <input id="additemid" type="text" class="form-control input-sm w-15 w-50" placeholder="item id" pattern="[0-9]+" required>
-        <input id="addattributes" type="text" class="form-control input-sm w-15" placeholder="attributes (comma separated)" pattern="[0-9a-zA-Z, ]*">
+        <input id="addattributes" type="text" class="form-control input-sm w-15" placeholder="attributes (comma separated)" pattern="[0-9a-zA-Z, \-]*">
         <button id="addbutton" class="btn btn-secondary" type="button">add</button>
       </div>
       <div class="btn-group mr-2" role="group" aria-label="Manage list group">