diff --git a/phys/module_mp_SBM_polar_radar.F b/phys/module_mp_SBM_polar_radar.F
index 4ee029a45a..4f94129271 100644
--- a/phys/module_mp_SBM_polar_radar.F
+++ b/phys/module_mp_SBM_polar_radar.F
@@ -1534,7 +1534,7 @@ subroutine calc_dc_wet_snow &
                     (1.0d0-(1.0d0-fract_volume_water)*ratc))
 ! new change 18.01.09                                         (start)
       if(fract_volume_water.gt.1.0d-10) then
-         t=derf((1.0d0-fract_volume_water)/fract_volume_water-0.2d0)
+         t=erf((1.0d0-fract_volume_water)/fract_volume_water-0.2d0)
       else
          t=1.0d0
       endif