diff --git a/Tools/autotest/param_metadata/param.py b/Tools/autotest/param_metadata/param.py
index b0b02c8e104..418f52d5eea 100644
--- a/Tools/autotest/param_metadata/param.py
+++ b/Tools/autotest/param_metadata/param.py
@@ -101,6 +101,9 @@ known_units = {
              'rad'     : 'radians'               ,
              'rad/s'   : 'radians per second'    ,
              'rad/s/s' : 'radians per square second' ,
+             's/rad'   : 'seconds per radian'    ,
+             '1/rad'   : 'per radian'            ,
+             's^2/rad' : 'seconds squared per radian',
 # electricity
              'A'       : 'ampere'                ,
              'V'       : 'volt'                  ,