diff --git a/editions/prerelease/tiddlers/system/SitePreviewUrl.tid b/editions/prerelease/tiddlers/system/SitePreviewUrl.tid
index e710389e7..0111c059f 100644
--- a/editions/prerelease/tiddlers/system/SitePreviewUrl.tid
+++ b/editions/prerelease/tiddlers/system/SitePreviewUrl.tid
@@ -1,3 +1,3 @@
 title: $:/SitePreviewUrl
 
-https://tiddlywiki.com/prerelease/images/Introduction%20Video%20Thumbnail.jpg
\ No newline at end of file
+https://tiddlywiki.com/prerelease/images/Introduction%2520Video%2520Thumbnail.jpg
\ No newline at end of file
diff --git a/editions/tw5.com/tiddlers/system/SitePreviewUrl.tid b/editions/tw5.com/tiddlers/system/SitePreviewUrl.tid
index 1f9f66551..6af0ba2e5 100644
--- a/editions/tw5.com/tiddlers/system/SitePreviewUrl.tid
+++ b/editions/tw5.com/tiddlers/system/SitePreviewUrl.tid
@@ -1,3 +1,3 @@
 title: $:/SitePreviewUrl
 
-https://tiddlywiki.com/images/Introduction%20Video%20Thumbnail.jpg
\ No newline at end of file
+https://tiddlywiki.com/images/Introduction%2520Video%2520Thumbnail.jpg
\ No newline at end of file