diff --git a/chrome/content/zotero-platform/win/overlay.css b/chrome/content/zotero-platform/win/overlay.css
index 464090cbc..b90ec7c58 100644
--- a/chrome/content/zotero-platform/win/overlay.css
+++ b/chrome/content/zotero-platform/win/overlay.css
@@ -78,6 +78,11 @@
 	border-width: 0 1px 1px 0;
 }
 
+/* Restore row highlighting on drag over, though I'm not sure how we're losing it to begin with. */
+#zotero-collections-tree treechildren::-moz-tree-row(dropOn) {
+	background-color: Highlight;
+}
+
 #zotero-items-tree {
 	border-width: 0 1px;
 }