diff --git a/src/DynamicModel.cc b/src/DynamicModel.cc
index cc5d7987fbc9368c00b453e3c0ad6aebf1f2a89b..ea1e6c05a9ce944e3eb607a63cf0650c2b43116b 100644
--- a/src/DynamicModel.cc
+++ b/src/DynamicModel.cc
@@ -4150,8 +4150,7 @@ 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);
 }