diff --git a/model/src/w3profsmd.F90 b/model/src/w3profsmd.F90
index b3f004d44..4b5f8c0ae 100644
--- a/model/src/w3profsmd.F90
+++ b/model/src/w3profsmd.F90
@@ -1266,7 +1266,7 @@ SUBROUTINE W3XYPFSNIMP ( ISP, C, LCALC, RD10, RD20, DT, AC)
       DO IBI=1, NBI
         IP    = MAPSF(ISBPI(IBI),1)
         AC(IP) = ( RD1*BBPI0(ISP,IBI) + RD2*BBPIN(ISP,IBI) )   &
-             *IOBPA(IP)*(1-IOBPD(ITH,IP)) / CG(IK,ISBPI(IBI)) * CLATS(ISBPI(IBI))
+             *IOBPA(IP)*IOBPD(ITH,IP) / CG(IK,ISBPI(IBI)) * CLATS(ISBPI(IBI))
       END DO
     END IF