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
@@ -17,6 +17,10 @@
 #include <__utility/move.h>
 #include <cstddef>
 
+#if _LIBCPP_STD_VER > 17
+#include <__ranges/access.h>
+#endif
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
@@ -36,8 +40,12 @@
 _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