Korean in calc

I have a problem with Korean (Hangul) not displaying in LibreOffice Calc

I have a spreadsheet containing texts in the following scripts: Latin, Chinese, Japanese, Korean, Arabic, Cyrillic, Hebrew, Devanagari, Thai, Greek.

All are formatted to display in DejaVu Sans.

All display correctly except for Korean, which shows up as box outlines.

If I copy these boxes and past into a text editor (I have tried Geany and gEdit), using DejaVu Sans, the Hangul characters are displayed correctly.

So the text is there in the spreadsheet, but is not correctly rendered.