diff --git a/include/boost/regex/v4/fileiter.hpp b/include/boost/regex/v4/fileiter.hpp
index 4873a0a8..256a7e46 100644
--- a/include/boost/regex/v4/fileiter.hpp
+++ b/include/boost/regex/v4/fileiter.hpp
@@ -225,11 +225,11 @@ public:
    mapfile_iterator() { node = 0; file = 0; offset = 0; }
    mapfile_iterator(const mapfile* f, long arg_position)
    {
+      BOOST_ASSERT(f);
       file = f;
       node = f->_first + arg_position / mapfile::buf_size;
       offset = arg_position % mapfile::buf_size;
-      if(file)
-         file->lock(node);
+      file->lock(node);
    }
    mapfile_iterator(const mapfile_iterator& i)
    {