diff --git a/F90subroutines/routing_reg.f90 b/F90subroutines/routing_reg.f90
index 2a21806882b161f665aba7398420cce234873177..57b0d017df7ef9353c87c95238a17e0ba8758222 100644
--- a/F90subroutines/routing_reg.f90
+++ b/F90subroutines/routing_reg.f90
@@ -2229,6 +2229,7 @@ SUBROUTINE routing_reg_linkup(nbpt, neighbours, nwbas, basin_count, basin_area,
              !
              IF ( found == 0 ) THEN
                 WRITE (numout,*) "Looking for a solution in the grid"
+                sbint = undef_int
                 DO sba=1,basin_count(sp)
                    IF ( sba .NE. sb ) THEN
                       IF ( basin_id(sp,sb) == basin_id(sp,sba) ) THEN