diff --git a/chrome/content/zotero-platform/mac/overlay.css b/chrome/content/zotero-platform/mac/overlay.css
index 10bd317a4..97de492b2 100644
--- a/chrome/content/zotero-platform/mac/overlay.css
+++ b/chrome/content/zotero-platform/mac/overlay.css
@@ -76,6 +76,21 @@
 	border-left: 1px solid transparent;
 }
 
+
+/* Firefox 55 changes */
+#zotero-toolbar-buttons[cui-areatype="toolbar"]:hover .toolbarbutton-menubutton-button,
+#zotero-toolbar-buttons[cui-areatype="toolbar"]:hover .toolbarbutton-menubutton-dropmarker,
+#zotero-toolbar-save-button[cui-areatype="toolbar"]:hover > .toolbarbutton-menubutton-button,
+#zotero-toolbar-save-button[cui-areatype="toolbar"]:hover > .toolbarbutton-menubutton-dropmarker {
+	border: 0 !important;
+}
+
+#zotero-toolbar-buttons[cui-areatype="toolbar"]:hover .dropmarker-icon,
+#zotero-toolbar-save-button[cui-areatype="toolbar"]:hover .dropmarker-icon {
+	padding-top: calc(var(--toolbarbutton-inner-padding) + 5px);
+	padding-bottom: calc(var(--toolbarbutton-inner-padding) + 5px);
+}
+
 /*
  * Alterations for overflow menu
  */