diff --git a/doc/container.qbk b/doc/container.qbk
index d7b8a1a..7b571dd 100644
--- a/doc/container.qbk
+++ b/doc/container.qbk
@@ -1413,6 +1413,7 @@ use [*Boost.Container]? There are several reasons for that:
 
 * Fixed bugs/issues:
    * [@https://github.com/boostorg/container/issues/232 GitHub #232: ['"Fix using pmr::polymorphic_allocator in pre-main"]].
+   * [@https://github.com/boostorg/container/issues/236 GitHub #236: ['"flat_tree::erase_unique uses wrong iterator"]].
 
 [endsect]
 
diff --git a/include/boost/container/detail/flat_tree.hpp b/include/boost/container/detail/flat_tree.hpp
index 6271974..3c20b56 100644
--- a/include/boost/container/detail/flat_tree.hpp
+++ b/include/boost/container/detail/flat_tree.hpp
@@ -1129,8 +1129,8 @@ class flat_tree
 
    size_type erase_unique(const key_type& k)
    {
-      iterator i = this->find(k);
-      size_type ret = static_cast<size_type>(i != this->end());
+      const_iterator i = static_cast<const flat_tree &>(*this).find(k);
+      size_type ret = static_cast<size_type>(i != this->cend());
       if (ret)
          this->erase(i);
       return ret;