Index: include/ostream
===================================================================
--- include/ostream
+++ include/ostream
@@ -218,6 +218,10 @@
     basic_ostream& operator<<(const void* __p);
     basic_ostream& operator<<(basic_streambuf<char_type, traits_type>* __sb);
 
+    _LIBCPP_INLINE_VISIBILITY
+    basic_ostream& operator<<(nullptr_t)
+    { return *this << static_cast<const char*>("nullptr\0"); }
+
     // 27.7.2.7 Unformatted output:
     basic_ostream& put(char_type __c);
     basic_ostream& write(const char_type* __s, streamsize __n);
Index: test/std/input.output/iostream.format/output.streams/ostream.formatted/ostream.inserters/streambuf.pass.cpp
===================================================================
--- test/std/input.output/iostream.format/output.streams/ostream.formatted/ostream.inserters/streambuf.pass.cpp
+++ test/std/input.output/iostream.format/output.streams/ostream.formatted/ostream.inserters/streambuf.pass.cpp
@@ -67,6 +67,13 @@
         os << &sb2;
         assert(sb.str() == "testing...");
     }
+    { // LWG 2221 - nullptr
+        testbuf<char> sb;
+        std::ostream os(&sb);
+        os << nullptr;
+        assert(sb.str().size() != 0);
+        LIBCPP_ASSERT(sb.str() == "nullptr");
+    }
 
   return 0;
 }