diff --git a/cfgs/SHARED/namelist_ref b/cfgs/SHARED/namelist_ref
index 4e241a48d84606275f48bd7ceb0498de99ca9d67..5c329d3aca36475e3b32fe3224e2aa7ccdc91705 100644
--- a/cfgs/SHARED/namelist_ref
+++ b/cfgs/SHARED/namelist_ref
@@ -232,8 +232,10 @@
    ln_dm2dc    = .false.   !  daily mean to diurnal cycle on short wave
    ln_ssr      = .false.   !  Sea Surface Restoring on T and/or S       (T => fill namsbc_ssr)
    nn_fwb      = 0         !  FreshWater Budget: =0 unchecked
-      !                    !     =1 global mean of e-p-r set to zero at each time step
-      !                    !     =2 annual global mean of e-p-r set to zero
+      !                    !     =1 volume set to zero at each time step
+      !                    !     =2 volume adjusted from previous year budget (uniform correction to emp)
+      !                    !     =3 volume adjusted from previous year budget (non-uniform correction - proportional to erp)
+      !                    !     =4 special treatment for ISOMIP+ test case
    ln_rnf      = .false.   !  runoffs                                   (T => fill namsbc_rnf)
    ln_apr_dyn  = .false.   !  Patm gradient added in ocean & ice Eqs.   (T => fill namsbc_apr )
    ln_wave     = .false.   !  Activate coupling with wave  (T => fill namsbc_wave)
diff --git a/src/OCE/SBC/sbcfwb.F90 b/src/OCE/SBC/sbcfwb.F90
index 616267af84f6e3405dbaee537b15da23abae2d6e..902a2061a3f04c96f84ab8f63a9443d36bedaf5e 100644
--- a/src/OCE/SBC/sbcfwb.F90
+++ b/src/OCE/SBC/sbcfwb.F90
@@ -130,8 +130,10 @@ CONTAINS
             CASE( 3 )
                WRITE(numout,*) '          nn_fwb = 3: Volume set to zero at each time step'
                WRITE(numout,*) '          => non-uniform correction proportional to erp'
+            CASE( 4 )
+               WRITE(numout,*) '          nn_fwb = 4: ISOMIP+ case'
             CASE DEFAULT
-               CALL ctl_stop( 'sbc_fwb : wrong nn_fwb value for the FreshWater Budget correction, choose either 1, 2 or 3' )
+               CALL ctl_stop( 'sbc_fwb : wrong nn_fwb value for the FreshWater Budget correction, choose either 1, 2, 3 or 4' )
             END SELECT
             !
             SELECT CASE ( nn_fwb_voltype )
@@ -505,7 +507,7 @@ CONTAINS
          ENDIF
          !
       CASE DEFAULT                           !==  you should never be there  ==!
-         CALL ctl_stop( 'sbc_fwb : wrong nn_fwb value for the FreshWater Budget correction, choose either 1, 2 or 3' )
+         CALL ctl_stop( 'sbc_fwb : wrong nn_fwb value for the FreshWater Budget correction, choose either 1, 2, 3 or 4' )
          !
       END SELECT
       !