diff --git a/libcxx/include/__iterator/insert_iterator.h b/libcxx/include/__iterator/insert_iterator.h
--- a/libcxx/include/__iterator/insert_iterator.h
+++ b/libcxx/include/__iterator/insert_iterator.h
@@ -14,6 +14,7 @@
 #include <__iterator/iterator.h>
 #include <__iterator/iterator_traits.h>
 #include <__memory/addressof.h>
+#include <__ranges/access.h>
 #include <__utility/move.h>
 #include <cstddef>
 
@@ -36,8 +37,12 @@
 _LIBCPP_SUPPRESS_DEPRECATED_POP
 protected:
     _Container* container;
-    typename _Container::iterator iter; // FIXME: `ranges::iterator_t<Container>` in C++20 mode
-public:
+#if _LIBCPP_STD_VER > 17
+    ranges::iterator_t<_Container> iter;
+#else
+    typename _Container::iterator iter;
+#endif
+  public:
     typedef output_iterator_tag iterator_category;
     typedef void value_type;
 #if _LIBCPP_STD_VER > 17