fix #107917

src/vs/workbench/contrib/notebook/browser/contrib/coreActions.ts

@@ -1483,7 +1483,7 @@ export class ChangeCellLanguageAction extends NotebookCellAction {
 		const selection = await quickInputService.pick(picks, { placeHolder: localize('pickLanguageToConfigure', "Select Language Mode") }) as ILanguagePickInput | undefined;
 		if (selection && selection.languageId) {
 			if (selection.languageId === 'markdown' && context.cell?.language !== 'markdown') {
-				const newCell = await changeCellToKind(CellKind.Markdown, { cell: context.cell, notebookEditor: context.notebookEditor });
+				const newCell = await changeCellToKind(CellKind.Markdown, { cell: context.cell, notebookEditor: context.notebookEditor }, 'markdown');
 				if (newCell) {
 					context.notebookEditor.focusNotebookCell(newCell, 'editor');
 				}