diff --git a/chrome/content/zotero-platform/mac/overlay.css b/chrome/content/zotero-platform/mac/overlay.css
index d7d32439a..bac52ea0b 100644
--- a/chrome/content/zotero-platform/mac/overlay.css
+++ b/chrome/content/zotero-platform/mac/overlay.css
@@ -347,10 +347,8 @@
 	background-color: #8b8b8b !important;
 }
 
-#zotero-collections-splitter[state=collapsed], #zotero-items-splitter[state=collapsed]
-{
-	border-right: 1px;
-	border-color: #A5A5A5;
+#zotero-collections-splitter[state=collapsed], #zotero-items-splitter[state=collapsed] {
+	border: 0 solid #d6d6d6 !important;
 	max-width: 8px !important;
 	min-width: 8px !important;
 	width: 8px !important;
@@ -359,6 +357,14 @@
 	padding: 0;
 }
 
+#zotero-collections-splitter[state=collapsed] {
+	border-right-width: 1px !important;
+}
+
+#zotero-items-splitter[state=collapsed] {
+	border-left-width: 1px !important;
+}
+
 #zotero-collections-splitter[state=collapsed] > grippy, #zotero-items-splitter[state=collapsed] > grippy
 {
 	-moz-appearance: none;