diff --git a/src/define_isostasy_bc.f90 b/src/define_isostasy_bc.f90
index 3f8ba11fa2c2f0873f6d2eeb9667f1397b977aaf..d9708bf147148064db049acb4a7d6f6ccdbe55e6 100644
--- a/src/define_isostasy_bc.f90
+++ b/src/define_isostasy_bc.f90
@@ -105,7 +105,7 @@ else
 
     ! Modify velocities
     if (osolve%z(i).lt.eps) then
-      if (osolve%x(i).le.x0) then
+      if (osolve%x(i).le.x0(i)) then
         if (spu.le.1.d0-eps) then                                               ! No change in B/Cs
           zdisp=osolve%u(i)*sin(atan(zsl))                                      ! Negative for negative slope
           vinit=(osolve%u(i)**2.d0+osolve%w(i)**2.d0)**0.5d0                    ! Incoming velocity vector magnitude