Topic on Extension talk:CollapsibleSections

Resolved by back-porting patches to supported branches

Error: Syntax error, unrecognized expression: unsupported pseudo: heading

I receive this error on every page with <h2> headers.

$wgCollapsibleSectionsEnableDesktop = true; - this is set.

Nothing is collapsible. Any suggestions?

WikiMedia 1.35.1

Which version of the extension are you using?