diff --git a/Source/wall.f90 b/Source/wall.f90
index cde923b1d90..8991b810ff7 100644
--- a/Source/wall.f90
+++ b/Source/wall.f90
@@ -1328,9 +1328,10 @@ SUBROUTINE CALCULATE_ZZ_F(T,DT,WALL_INDEX,CFACE_INDEX,PARTICLE_INDEX)
 ! Only set species mass fraction in the ghost cell if it is not solid
 
 IF (PRESENT(WALL_INDEX)) THEN
-   IF (WALL_INDEX<=N_EXTERNAL_WALL_CELLS .AND. .NOT.CELL(IC)%SOLID .AND. .NOT.CELL(ICG)%SOLID) &
-       ZZP(BC%II,BC%JJ,BC%KK,1:N_TRACKED_SPECIES) = 2._EB*B1%ZZ_F(1:N_TRACKED_SPECIES) - B1%ZZ_G(1:N_TRACKED_SPECIES)
-       ZZP(BC%II2,BC%JJ2,BC%KK2,1:N_TRACKED_SPECIES) = 2._EB*B1%ZZ_F(1:N_TRACKED_SPECIES) - B1%ZZ_G(1:N_TRACKED_SPECIES)
+   IF (WALL_INDEX<=N_EXTERNAL_WALL_CELLS .AND. .NOT.CELL(IC)%SOLID .AND. .NOT.CELL(ICG)%SOLID) THEN
+      ZZP(BC%II,BC%JJ,BC%KK,1:N_TRACKED_SPECIES)    = 2._EB*B1%ZZ_F(1:N_TRACKED_SPECIES) - B1%ZZ_G(1:N_TRACKED_SPECIES)
+      ZZP(BC%II2,BC%JJ2,BC%KK2,1:N_TRACKED_SPECIES) = 2._EB*B1%ZZ_F(1:N_TRACKED_SPECIES) - B1%ZZ_G(1:N_TRACKED_SPECIES)
+   ENDIF
 ENDIF
 
 END SUBROUTINE CALCULATE_ZZ_F