diff --git a/code/ysolve.f90 b/code/ysolve.f90
index 3bbab83..4ed1c61 100644
--- a/code/ysolve.f90
+++ b/code/ysolve.f90
@@ -670,6 +670,7 @@
      REAL FUNCTION diffusivity_sutherland(c)
          REAL, INTENT(IN) :: c
          REAL :: theta, As, Ts, T0, T1
+         REAL, PARAMETER :: rvis=5.0d0
          T0 = 1.0
          T1 = (1.0 + bc)