--- a/eric6/UI/Previewers/PreviewerHTML.py Mon Apr 12 18:25:52 2021 +0200 +++ b/eric6/UI/Previewers/PreviewerHTML.py Mon Apr 12 19:05:23 2021 +0200 @@ -688,10 +688,12 @@ extensions = [] mermaidNeeded = False - if Preferences.getEditor("PreviewMarkdownMermaid"): - if MarkdownExtensions.MermaidRegexFullText.search(text): - extensions.append(MarkdownExtensions.MermaidExtension()) - mermaidNeeded = True + if ( + Preferences.getEditor("PreviewMarkdownMermaid") and + MarkdownExtensions.MermaidRegexFullText.search(text) + ): + extensions.append(MarkdownExtensions.MermaidExtension()) + mermaidNeeded = True if convertNewLineToBreak: extensions.append('nl2br')