diff --git a/libcxx/include/__debug b/libcxx/include/__debug
--- a/libcxx/include/__debug
+++ b/libcxx/include/__debug
@@ -12,7 +12,6 @@
 
 #include <__assert>
 #include <__config>
-#include <iosfwd>
 #include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/experimental/iterator b/libcxx/include/experimental/iterator
--- a/libcxx/include/experimental/iterator
+++ b/libcxx/include/experimental/iterator
@@ -57,6 +57,7 @@
 #include <__utility/forward.h>
 #include <__utility/move.h>
 #include <experimental/__config>
+#include <iosfwd> // char_traits
 #include <iterator>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
diff --git a/libcxx/include/module.modulemap b/libcxx/include/module.modulemap
--- a/libcxx/include/module.modulemap
+++ b/libcxx/include/module.modulemap
@@ -619,6 +619,7 @@
   }
   module iterator {
     header "iterator"
+    export iosfwd
     export *
 
     module __iterator {