diff --git a/src/encounter/encounter_check.f90 b/src/encounter/encounter_check.f90
index 6e5e11c88..749252d54 100644
--- a/src/encounter/encounter_check.f90
+++ b/src/encounter/encounter_check.f90
@@ -1112,10 +1112,11 @@ subroutine sweep_dl(i, n1, n2, ntot, ext_ind, ibegi, iendi, ibeg, iend, lencount
 
             lencounteri(:) = .false.
             lencounterj(jlo:jhi) = .false.
-            box(:) = ext_ind(jlo:jhi)
 
-            where(box(jlo:jhi) > ntot)
-               box(jlo:jhi) = box(jlo:jhi) - ntot
+            where(ext_ind(jlo:jhi) > ntot)
+               box(jlo:jhi) = ext_ind(jlo:jhi) - ntot
+            elsewhere
+               box(jlo:jhi) = ext_ind(jlo:jhi)
             endwhere
 
             call timer1%stop()
@@ -1215,10 +1216,11 @@ pure subroutine sweep_sl(n, ext_ind, ibegi, iendi, ibeg, iend, lencounteri)
 
             lencounteri(:) = .false.
             lencounterj(jlo:jhi) = .false.
-            box(:) = ext_ind(jlo:jhi)
 
-            where(box(:) > n)
-               box(:) = box(:) - n
+            where(ext_ind(jlo:jhi) > n)
+               box(jlo:jhi) = ext_ind(jlo:jhi) - n
+            elsewhere
+               box(jlo:jhi) = ext_ind(jlo:jhi)
             endwhere
 
             ibegy(jlo:jhi) = ibeg(2,box(jlo:jhi))