--- a/browser/extensions/formautofill/content/formautofill.css
+++ b/browser/extensions/formautofill/content/formautofill.css
@@ -7,11 +7,17 @@
   margin: 0;
   padding: 0;
   height: auto;
   min-height: auto;
 
   -moz-binding: url("chrome://formautofill/content/formautofill.xml#autocomplete-profile-listitem");
 }
 
+/* Treat @collpased="true" as display: none similar to how it is for XUL elements.
+ * https://developer.mozilla.org/en-US/docs/Web/CSS/visibility#Values */
+#PopupAutoComplete > richlistbox > richlistitem[originaltype="autofill-profile"][collapsed="true"] {
+  display: none;
+}
+
 #PopupAutoComplete[firstresultstyle="autofill-profile"] {
   min-width: 150px !important;
 }