--- a/prosodyctl	Sat Mar 03 20:55:46 2018 +0100
+++ b/prosodyctl	Tue Mar 06 01:45:58 2018 +0100
@@ -866,7 +866,7 @@
 	assert(input:close());
 	assert(output:close());
 	if owner and group then
-		local ok = os.execute(("chown %s.%s %s"):format(sh_esc(owner), sh_esc(group), sh_esc(to)));
+		local ok = os.execute(("chown %s:%s %s"):format(sh_esc(owner), sh_esc(group), sh_esc(to)));
 		assert(ok == true or ok == 0, "Failed to change ownership of "..to);
 	end
 	if old_umask then pposix.umask(old_umask); end