diff --git a/doc/Makefile b/doc/Makefile
index 3fc092ccae4bd..d1c6ff87f0dea 100644
--- a/doc/Makefile
+++ b/doc/Makefile
@@ -26,7 +26,7 @@ DOCUMENTER_OPTIONS := linkcheck=$(linkcheck) doctest=$(doctest) buildroot=$(call
 
 $(SRCCACHE)/UnicodeData.txt:
 	@mkdir -p "$(SRCCACHE)"
-	$(JLDOWNLOAD) "$@" http://www.unicode.org/Public/9.0.0/ucd/UnicodeData.txt
+	$(JLDOWNLOAD) "$@" http://www.unicode.org/Public/12.1.0/ucd/UnicodeData.txt
 
 deps: $(SRCCACHE)/UnicodeData.txt
 	$(JLCHECKSUM) "$<"