diff --git a/css/default.css b/css/default.css
index 9d6b81fd1..e83631c19 100644
--- a/css/default.css
+++ b/css/default.css
@@ -1762,6 +1762,7 @@ body.ttrss_utility.share_popup .content {
 }
 .flat .dijitTree .dijitTreeRow {
   overflow: hidden;
+  -moz-user-select: none; /* TODO: temporary workaround for bug: https://discourse.tt-rss.org/t/is-it-possible-to-create-a-hierarchy-of-categories/876/13 */
   text-overflow: ellipsis;
 }
 .flat label.dijitButton {
diff --git a/css/dijit_basic.less b/css/dijit_basic.less
index 7c13eff84..4609333c4 100644
--- a/css/dijit_basic.less
+++ b/css/dijit_basic.less
@@ -132,6 +132,7 @@
 
 		.dijitTreeRow {
 			overflow: hidden;
+			-moz-user-select: none; /* TODO: temporary workaround for bug: https://discourse.tt-rss.org/t/is-it-possible-to-create-a-hierarchy-of-categories/876/13 */
 			text-overflow: ellipsis;
 		}