diff --git a/core/ui/PageTemplate/sidebar.tid b/core/ui/PageTemplate/sidebar.tid
index d202db60e..7d85129a4 100644
--- a/core/ui/PageTemplate/sidebar.tid
+++ b/core/ui/PageTemplate/sidebar.tid
@@ -6,7 +6,7 @@ $:/config/PageControlButtons/Visibility/$(listItem)$
 \end
 <$scrollable fallthrough="no" class="tw-sidebar-scrollable">
 
-<div class="sidebar-header">
+<div class="tc-sidebar-header">
 
 <$reveal state="$:/state/sidebar" type="match" text="yes" default="yes" retain="yes">
 
diff --git a/themes/tiddlywiki/snowwhite/base.tid b/themes/tiddlywiki/snowwhite/base.tid
index 5a93f2b3e..7a64693c7 100644
--- a/themes/tiddlywiki/snowwhite/base.tid
+++ b/themes/tiddlywiki/snowwhite/base.tid
@@ -3,7 +3,7 @@ tags: [[$:/tags/stylesheet]]
 
 \rules only filteredtranscludeinline transcludeinline macrodef macrocallinline
 
-.sidebar-header {
+.tc-sidebar-header {
 	text-shadow: 0 1px 0 <<colour sidebar-foreground-shadow>>;
 }
 
diff --git a/themes/tiddlywiki/vanilla/base.tid b/themes/tiddlywiki/vanilla/base.tid
index 2ebcee7cc..23a3b3783 100644
--- a/themes/tiddlywiki/vanilla/base.tid
+++ b/themes/tiddlywiki/vanilla/base.tid
@@ -371,21 +371,21 @@ button.tw-tag-label, span.tw-tag-label {
 	fill: <<colour foreground>>;
 }
 
-.sidebar-header {
+.tc-sidebar-header {
 	color: <<colour sidebar-foreground>>;
 	fill: <<colour sidebar-foreground>>;
 }
 
-.sidebar-header .tc-title a.tw-tiddlylink-resolves {
+.tc-sidebar-header .tc-title a.tw-tiddlylink-resolves {
 	font-weight: 300;
 }
 
-.sidebar-header .tw-sidebar-lists p {
+.tc-sidebar-header .tw-sidebar-lists p {
 	margin-top: 3px;
 	margin-bottom: 3px;
 }
 
-.sidebar-header .tw-missing-tiddler-label {
+.tc-sidebar-header .tw-missing-tiddler-label {
 	color: <<colour sidebar-foreground>>;
 }
 
@@ -453,7 +453,7 @@ button.tw-tag-label, span.tw-tag-label {
 
 @media (max-width: {{$:/themes/tiddlywiki/vanilla/metrics/sidebarbreakpoint}}) {
 
-	.sidebar-header {
+	.tc-sidebar-header {
 		padding: 14px;
 		min-height: 32px;
 	}
@@ -507,7 +507,7 @@ button.tw-tag-label, span.tw-tag-label {
 		background-color: transparent;
 	}
 
-	.sidebar-header, .tw-topbar {
+	.tc-sidebar-header, .tw-topbar {
 		display: none;
 	}