diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 1020c19f0bef..6003a00fdf04 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,8 @@
+2012-03-27  Jonathan Wakely  <jwakely.gcc@gmail.com>
+
+	* include/std/functional (mem_fn): Qualify to prevent ADL.
+	* testsuite/20_util/function_objects/mem_fn/adl.cc: New.
+
 2012-03-27  Jonathan Wakely  <jwakely.gcc@gmail.com>
 
 	* include/std/type_traits (result_of): Fix handling of cv-quals.
diff --git a/libstdc++-v3/include/std/functional b/libstdc++-v3/include/std/functional
index 4be1bc793f36..14785dd57b73 100644
--- a/libstdc++-v3/include/std/functional
+++ b/libstdc++-v3/include/std/functional
@@ -1,7 +1,7 @@
 // <functional> -*- C++ -*-
 
 // Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
-// 2011 Free Software Foundation, Inc.
+// 2011, 2012 Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
 // software; you can redistribute it and/or modify it under the
@@ -245,7 +245,7 @@ _GLIBCXX_HAS_NESTED_TYPE(result_type)
            >::type
     __invoke(_Functor& __f, _Args&&... __args)
     {
-      return mem_fn(__f)(std::forward<_Args>(__args)...);
+      return std::mem_fn(__f)(std::forward<_Args>(__args)...);
     }
 
   // To pick up function references (that will become function pointers)
@@ -1709,12 +1709,12 @@ _GLIBCXX_HAS_NESTED_TYPE(result_type)
   template<typename _Member, typename _Class>
     inline _Mem_fn<_Member _Class::*>
     __callable_functor(_Member _Class::* &__p)
-    { return mem_fn(__p); }
+    { return std::mem_fn(__p); }
 
   template<typename _Member, typename _Class>
     inline _Mem_fn<_Member _Class::*>
     __callable_functor(_Member _Class::* const &__p)
-    { return mem_fn(__p); }
+    { return std::mem_fn(__p); }
 
   template<typename _Signature>
     class function;
@@ -1970,7 +1970,7 @@ _GLIBCXX_HAS_NESTED_TYPE(result_type)
       static _Res
       _M_invoke(const _Any_data& __functor, _ArgTypes... __args)
       {
-	return mem_fn(_Base::_M_get_pointer(__functor)->__value)(
+	return std::mem_fn(_Base::_M_get_pointer(__functor)->__value)(
 	    std::forward<_ArgTypes>(__args)...);
       }
     };
@@ -2010,7 +2010,7 @@ _GLIBCXX_HAS_NESTED_TYPE(result_type)
       static void
       _M_invoke(const _Any_data& __functor, _ArgTypes... __args)
       {
-	mem_fn(_Base::_M_get_pointer(__functor)->__value)(
+	std::mem_fn(_Base::_M_get_pointer(__functor)->__value)(
 	    std::forward<_ArgTypes>(__args)...);
       }
     };
diff --git a/libstdc++-v3/testsuite/20_util/function_objects/mem_fn/adl.cc b/libstdc++-v3/testsuite/20_util/function_objects/mem_fn/adl.cc
new file mode 100644
index 000000000000..907db848911f
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/function_objects/mem_fn/adl.cc
@@ -0,0 +1,44 @@
+// { dg-options "-std=gnu++0x" }
+// { dg-do compile }
+
+// Copyright (C) 2012 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+#include <functional>
+
+namespace n {
+  struct X { int i; };
+  void mem_fn(int X::*);
+}
+
+using n::X;
+
+X x{};
+int X::* p = &X::i;
+
+int test01()
+{
+  auto ref = std::ref(p);
+  return ref(x);
+}
+
+int test02()
+{
+  std::function<int(X)> fun(p);
+  return fun(x);
+}
+