diff --git a/src/DynamicModel.cc b/src/DynamicModel.cc
index 29fa86d746aa5d9102ec71212d05fa170b45e6ec..32365f150ee3ba6ccbeb8c25c6fceec171d388d8 100644
--- a/src/DynamicModel.cc
+++ b/src/DynamicModel.cc
@@ -4397,8 +4397,7 @@ DynamicModel::OccbinRegimeTracker::checkAllRegimesPresent() const
       if (it == r.end())
         break;
       *it = true;
-      if (it != r.begin())
-        fill(r.begin(), prev(it), false);
+      fill(r.begin(), it, false);
     }
   while (true);
 }