diff --git a/doc/3.io-files.md b/doc/3.io-files.md
index 3f70230..a33d258 100644
--- a/doc/3.io-files.md
+++ b/doc/3.io-files.md
@@ -525,9 +525,9 @@ Variable         Type          Units   Definition
 `stmx`           Real        cm        Path from the launching point and peak $dP/dV$
                                        for the central ray.
 
-`psipol`         Real        ??        $\psi$ polarisation angle at vacuum-plasma boundary.
+`psipol`         Real        deg       $\psi$ polarisation angle at vacuum-plasma boundary.
 
-`chipol`         Real        ??        $\chi$ polarisation angle at vacuum-plasma boundary.
+`chipol`         Real        deg       $\chi$ polarisation angle at vacuum-plasma boundary.
 
 `index_rt`       Integer               Index encoding mode and pass number, see [@sec:index_rt].
 ---------------------------------------------------------------------------------------------------