diff --git a/src/crater/module_crater.f90 b/src/crater/module_crater.f90
index a5433e04..b6af42c8 100644
--- a/src/crater/module_crater.f90
+++ b/src/crater/module_crater.f90
@@ -241,11 +241,11 @@ end subroutine crater_make_list
    end interface
 
    interface
-      function crater_critical_slope(user,crater,iradsq) result(critical)
+      function crater_critical_slope(user,crater,lrad) result(critical)
       use module_globals
       type(usertype),intent(in) :: user
       type(cratertype),intent(in) :: crater
-      integer(I4B),intent(in) :: iradsq
+      real(DP),intent(in) :: lrad
       real(DP) :: critical
       end function crater_critical_slope
    end interface