diff -u b/core/themes/bartik/css/components/form.css b/core/themes/bartik/css/components/form.css
--- b/core/themes/bartik/css/components/form.css
+++ b/core/themes/bartik/css/components/form.css
@@ -63,6 +63,9 @@
 select {
   font-family: "Lucida Grande", "Lucida Sans Unicode", Verdana, sans-serif;
 }
+select {
+  max-width: 100%;
+}
 input {
   margin: 2px 0;
   padding: 4px;