diff --git a/src/cell.h b/src/cell.h
index c98913bfae2467c436efc5b6a8f44804e0ff8ef7..7c80e4c25a4337737180aa18a543e7da6d312eb3 100644
--- a/src/cell.h
+++ b/src/cell.h
@@ -341,7 +341,7 @@ struct cell {
   char do_sub_drift;
   
   /*! Bit mask of sorts that need to be computed for this cell. */
-  int do_sort;
+  unsigned int do_sort;
   
   /*! Do any of this cell's sub-cells need to be sorted? */
   char do_sub_sort;