diff --git a/lib/redmine/wiki_formatting/markdown/helper.rb b/lib/redmine/wiki_formatting/markdown/helper.rb
index fac2f8bf3..fb9f1a939 100644
--- a/lib/redmine/wiki_formatting/markdown/helper.rb
+++ b/lib/redmine/wiki_formatting/markdown/helper.rb
@@ -22,7 +22,7 @@ module Redmine
         def wikitoolbar_for(field_id, preview_url = preview_text_path)
           heads_for_wiki_formatter
           url = "#{Redmine::Utils.relative_url_root}/help/#{current_language.to_s.downcase}/wiki_syntax_markdown.html"
-          javascript_tag("var wikiToolbar = new jsToolBar(document.getElementById('#{field_id}')); wikiToolbar.setHelpLink('#{escape_javascript url}'); wikiToolbar.setPreviewUrl('#{preview_url}'); wikiToolbar.draw();")
+          javascript_tag("var wikiToolbar = new jsToolBar(document.getElementById('#{field_id}')); wikiToolbar.setHelpLink('#{escape_javascript url}'); wikiToolbar.setPreviewUrl('#{escape_javascript preview_url}'); wikiToolbar.draw();")
         end
 
         def initial_page_content(page)
diff --git a/lib/redmine/wiki_formatting/textile/helper.rb b/lib/redmine/wiki_formatting/textile/helper.rb
index 6e8ba9812..e536a29dc 100644
--- a/lib/redmine/wiki_formatting/textile/helper.rb
+++ b/lib/redmine/wiki_formatting/textile/helper.rb
@@ -23,7 +23,7 @@ module Redmine
           heads_for_wiki_formatter
           # Is there a simple way to link to a public resource?
           url = "#{Redmine::Utils.relative_url_root}/help/#{current_language.to_s.downcase}/wiki_syntax_textile.html"
-          javascript_tag("var wikiToolbar = new jsToolBar(document.getElementById('#{field_id}')); wikiToolbar.setHelpLink('#{escape_javascript url}'); wikiToolbar.setPreviewUrl('#{preview_url}'); wikiToolbar.draw();")
+          javascript_tag("var wikiToolbar = new jsToolBar(document.getElementById('#{field_id}')); wikiToolbar.setHelpLink('#{escape_javascript url}'); wikiToolbar.setPreviewUrl('#{escape_javascript preview_url}'); wikiToolbar.draw();")
         end
 
         def initial_page_content(page)