diff --git a/core/ui/PageTemplate/sidebar-resizer.tid b/core/ui/PageTemplate/sidebar-resizer.tid
index cad0f2123..6ddf05ac7 100644
--- a/core/ui/PageTemplate/sidebar-resizer.tid
+++ b/core/ui/PageTemplate/sidebar-resizer.tid
@@ -2,7 +2,7 @@ title: $:/core/ui/PageTemplate/sidebar-resizer
 tags: $:/tags/PageTemplate
 list-after: $:/core/ui/PageTemplate/story
 
-\import [function[get.base.functions.theme],<get.current.theme>first[]!is[missing]] :else[function[get.base.functions.theme],<get.current.theme>first[]is[shadow]] :else[[$:/themes/tiddlywiki/vanilla/functions]] [[$:/core/procedures/sidebar-resizer]]
+\import [function[get.base.functions.theme],<get.current.theme>first[]is[tiddler]] :else[function[get.base.functions.theme],<get.current.theme>first[]is[shadow]] :else[[$:/themes/tiddlywiki/vanilla/functions]] [[$:/core/procedures/sidebar-resizer]]
 \function resizer.state.tiddler() $:/state/sidebar/resizing
 \function resizer.state() [{$:/state/sidebar}]
 \function resizer.class() tc-main-sidebar-resizer
diff --git a/themes/tiddlywiki/vanilla/sidebar-resizer.tid b/themes/tiddlywiki/vanilla/sidebar-resizer.tid
index 1859e5f69..d893eae45 100644
--- a/themes/tiddlywiki/vanilla/sidebar-resizer.tid
+++ b/themes/tiddlywiki/vanilla/sidebar-resizer.tid
@@ -2,7 +2,7 @@ title: $:/themes/tiddlywiki/vanilla/sidebar-resizer
 tags: [[$:/tags/Stylesheet]]
 code-body: yes
 
-\import [function[get.base.functions.theme],<get.current.theme>first[]!is[missing]] :else[function[get.base.functions.theme],<get.current.theme>first[]is[shadow]] :else[[$:/themes/tiddlywiki/vanilla/functions]]
+\import [function[get.base.functions.theme],<get.current.theme>first[]is[tiddler]] :else[function[get.base.functions.theme],<get.current.theme>first[]is[shadow]] :else[[$:/themes/tiddlywiki/vanilla/functions]]
 
 \rules only filteredtranscludeinline transcludeinline macrodef macrocallinline macrocallblock conditional html