diff --git a/.travis.yml b/.travis.yml
index bd99c4f..9c1d6ff 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -28,6 +28,7 @@ matrix:
 
   include:
     - os: linux
+      compiler: g++-4.7
       env: TOOLSET=gcc COMPILER=g++-4.7 CXXSTD=c++11
       addons:
         apt:
@@ -37,6 +38,7 @@ matrix:
             - ubuntu-toolchain-r-test
 
     - os: linux
+      compiler: g++-4.8
       env: TOOLSET=gcc COMPILER=g++-4.8 CXXSTD=c++11
       addons:
         apt:
@@ -46,6 +48,7 @@ matrix:
             - ubuntu-toolchain-r-test
 
     - os: linux
+      compiler: g++-4.9
       env: TOOLSET=gcc COMPILER=g++-4.9 CXXSTD=c++11
       addons:
         apt:
@@ -55,6 +58,7 @@ matrix:
             - ubuntu-toolchain-r-test
 
     - os: linux
+      compiler: g++-5
       env: TOOLSET=gcc COMPILER=g++-5 CXXSTD=c++11
       addons:
         apt:
@@ -64,6 +68,7 @@ matrix:
             - ubuntu-toolchain-r-test
 
     - os: linux
+      compiler: g++-5
       env: TOOLSET=gcc COMPILER=g++-5 CXXSTD=c++14
       addons:
         apt:
@@ -73,6 +78,17 @@ matrix:
             - ubuntu-toolchain-r-test
 
     - os: linux
+      compiler: g++-5
+      env: TOOLSET=gcc COMPILER=g++-5 CXXSTD=c++1z
+      addons:
+        apt:
+          packages:
+            - g++-5
+          sources:
+            - ubuntu-toolchain-r-test
+
+    - os: linux
+      compiler: g++-6
       env: TOOLSET=gcc COMPILER=g++-6 CXXSTD=c++11
       addons:
         apt:
@@ -82,6 +98,7 @@ matrix:
             - ubuntu-toolchain-r-test
 
     - os: linux
+      compiler: g++-6
       env: TOOLSET=gcc COMPILER=g++-6 CXXSTD=c++14
       addons:
         apt:
@@ -91,6 +108,7 @@ matrix:
             - ubuntu-toolchain-r-test
 
     - os: linux
+      compiler: g++-6
       env: TOOLSET=gcc COMPILER=g++-6 CXXSTD=c++1z
       addons:
         apt:
@@ -100,6 +118,40 @@ matrix:
             - ubuntu-toolchain-r-test
 
     - os: linux
+      dist: trusty
+      compiler: g++-7
+      env: TOOLSET=gcc COMPILER=g++-7 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - g++-7
+          sources:
+            - ubuntu-toolchain-r-test
+
+    - os: linux
+      dist: trusty
+      compiler: g++-7
+      env: TOOLSET=gcc COMPILER=g++-7 CXXSTD=c++14
+      addons:
+        apt:
+          packages:
+            - g++-7
+          sources:
+            - ubuntu-toolchain-r-test
+
+    - os: linux
+      dist: trusty
+      compiler: g++-7
+      env: TOOLSET=gcc COMPILER=g++-7 CXXSTD=c++1z
+      addons:
+        apt:
+          packages:
+            - g++-7
+          sources:
+            - ubuntu-toolchain-r-test
+
+    - os: linux
+      compiler: clang++-3.5
       env: TOOLSET=clang COMPILER=clang++-3.5 CXXSTD=c++11
       addons:
         apt:
@@ -110,6 +162,7 @@ matrix:
             - llvm-toolchain-precise-3.5
 
     - os: linux
+      compiler: clang++-3.6
       env: TOOLSET=clang COMPILER=clang++-3.6 CXXSTD=c++11
       addons:
         apt:
@@ -120,6 +173,7 @@ matrix:
             - llvm-toolchain-precise-3.6
 
     - os: linux
+      compiler: clang++-3.7
       env: TOOLSET=clang COMPILER=clang++-3.7 CXXSTD=c++11
       addons:
         apt:
@@ -130,6 +184,7 @@ matrix:
             - llvm-toolchain-precise-3.7
 
     - os: linux
+      compiler: clang++-3.8
       env: TOOLSET=clang COMPILER=clang++-3.8 CXXSTD=c++11
       addons:
         apt:
@@ -140,6 +195,7 @@ matrix:
             - llvm-toolchain-precise-3.8
 
     - os: linux
+      compiler: clang++-3.8
       env: TOOLSET=clang COMPILER=clang++-3.8 CXXSTD=c++14
       addons:
         apt:
@@ -150,6 +206,7 @@ matrix:
             - llvm-toolchain-precise-3.8
 
     - os: linux
+      compiler: clang++-3.8
       env: TOOLSET=clang COMPILER=clang++-3.8 CXXSTD=c++1z
       addons:
         apt:
@@ -160,6 +217,7 @@ matrix:
             - llvm-toolchain-precise-3.8
 
     - os: linux
+      compiler: clang++-3.9
       env: TOOLSET=clang COMPILER=clang++-3.9 CXXSTD=c++11
       addons:
         apt:
@@ -170,6 +228,7 @@ matrix:
             - llvm-toolchain-precise-3.9
 
     - os: linux
+      compiler: clang++-3.9
       env: TOOLSET=clang COMPILER=clang++-3.9 CXXSTD=c++14
       addons:
         apt:
@@ -180,6 +239,7 @@ matrix:
             - llvm-toolchain-precise-3.9
 
     - os: linux
+      compiler: clang++-3.9
       env: TOOLSET=clang COMPILER=clang++-3.9 CXXSTD=c++1z
       addons:
         apt:
@@ -189,13 +249,49 @@ matrix:
             - ubuntu-toolchain-r-test
             - llvm-toolchain-precise-3.9
 
+    - os: linux
+      compiler: clang++-4.0
+      env: TOOLSET=clang COMPILER=clang++-4.0 CXXSTD=c++11
+      addons:
+        apt:
+          packages:
+            - clang-4.0
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-trusty-4.0
+
+    - os: linux
+      compiler: clang++-4.0
+      env: TOOLSET=clang COMPILER=clang++-4.0 CXXSTD=c++14
+      addons:
+        apt:
+          packages:
+            - clang-4.0
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-trusty-4.0
+
+    - os: linux
+      compiler: clang++-4.0
+      env: TOOLSET=clang COMPILER=clang++-4.0 CXXSTD=c++1z
+      addons:
+        apt:
+          packages:
+            - clang-4.0
+          sources:
+            - ubuntu-toolchain-r-test
+            - llvm-toolchain-trusty-4.0
+
     - os: osx
+      compiler: clang++
       env: TOOLSET=clang COMPILER=clang++ CXXSTD=c++11
 
     - os: osx
+      compiler: clang++
       env: TOOLSET=clang COMPILER=clang++ CXXSTD=c++14
 
     - os: osx
+      compiler: clang++
       env: TOOLSET=clang COMPILER=clang++ CXXSTD=c++1z
 
 install:
diff --git a/doc/html/mp11.html b/doc/html/mp11.html
index 06276b0..2c2c378 100644
--- a/doc/html/mp11.html
+++ b/doc/html/mp11.html
@@ -2029,7 +2029,7 @@
 </pre>
 <p>
           <code class="computeroutput"><span class="identifier">mp_for_each</span><span class="special">&lt;</span><span class="identifier">L</span><span class="special">&gt;(</span><span class="identifier">f</span><span class="special">)</span></code> calls
-          <code class="computeroutput"><span class="identifier">f</span></code> with <code class="computeroutput"><span class="identifier">mp_identity</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;()</span></code> for each element <code class="computeroutput"><span class="identifier">T</span></code>
+          <code class="computeroutput"><span class="identifier">f</span></code> with <code class="computeroutput"><span class="identifier">T</span><span class="special">()</span></code> for each element <code class="computeroutput"><span class="identifier">T</span></code>
           of the list <code class="computeroutput"><span class="identifier">L</span></code>, in order.
         </p>
 <p>
@@ -2504,7 +2504,7 @@
 </div>
 </div>
 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
-<td align="left"><p><small>Last revised: May 25, 2017 at 18:31:25 GMT</small></p></td>
+<td align="left"><p><small>Last revised: May 28, 2017 at 23:51:44 GMT</small></p></td>
 <td align="right"><div class="copyright-footer"></div></td>
 </tr></table>
 <hr>
diff --git a/doc/mp11/algorithm.qbk b/doc/mp11/algorithm.qbk
index 9f603f9..08f7a53 100644
--- a/doc/mp11/algorithm.qbk
+++ b/doc/mp11/algorithm.qbk
@@ -284,7 +284,7 @@ is `mp_size<L>`.
 [section `mp_for_each<L>(f)`]
     template<class L, class F> constexpr F mp_for_each(F&& f);
 
-`mp_for_each<L>(f)` calls `f` with `mp_identity<T>()` for each element `T` of the list `L`, in order.
+`mp_for_each<L>(f)` calls `f` with `T()` for each element `T` of the list `L`, in order.
 
 Returns `std::forward<F>(f)`.
 [endsect]
diff --git a/include/boost/mp11/algorithm.hpp b/include/boost/mp11/algorithm.hpp
index 0f68974..5d27cba 100644
--- a/include/boost/mp11/algorithm.hpp
+++ b/include/boost/mp11/algorithm.hpp
@@ -325,8 +325,8 @@ template<class L, std::size_t I> struct mp_at_c_impl
 
 } // namespace detail
 
-template<class L, std::size_t I> using mp_at_c = typename detail::mp_at_c_impl<L, I>::type;
-template<class L, class I> using mp_at = typename detail::mp_at_c_impl<L, std::size_t{ I::value }>::type;
+template<class L, std::size_t I> using mp_at_c = typename mp_if_c<(I < mp_size<L>::value), detail::mp_at_c_impl<L, I>, void>::type;
+template<class L, class I> using mp_at = mp_at_c<L, std::size_t{ I::value }>;
 
 // mp_take(_c)<L, N>
 namespace detail
@@ -882,7 +882,7 @@ namespace detail
 template<class... T, class F> BOOST_CONSTEXPR F mp_for_each_impl( mp_list<T...>, F && f )
 {
     using A = int[sizeof...(T)];
-    return (void)A{ ((void)f(mp_identity<T>()), 0)... }, std::forward<F>(f);
+    return (void)A{ ((void)f(T()), 0)... }, std::forward<F>(f);
 }
 
 #if BOOST_WORKAROUND( BOOST_MSVC, <= 1800 )
diff --git a/test/Jamfile.v2 b/test/Jamfile.v2
index 2d6df0a..b086740 100644
--- a/test/Jamfile.v2
+++ b/test/Jamfile.v2
@@ -48,6 +48,7 @@ run mp_product.cpp : : : $(REQ) ;
 run mp_drop.cpp : : : $(REQ) ;
 run mp_iota.cpp : : : $(REQ) ;
 run mp_at.cpp : : : $(REQ) ;
+run mp_at_sf.cpp : : : $(REQ) ;
 run mp_take.cpp : : : $(REQ) ;
 run mp_replace.cpp : : : $(REQ) ;
 run mp_replace_if.cpp : : : $(REQ) ;
diff --git a/test/mp_at_sf.cpp b/test/mp_at_sf.cpp
new file mode 100644
index 0000000..00463f9
--- /dev/null
+++ b/test/mp_at_sf.cpp
@@ -0,0 +1,39 @@
+
+// Copyright 2015, 2017 Peter Dimov.
+//
+// Distributed under the Boost Software License, Version 1.0.
+//
+// See accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
+
+#include <boost/mp11/utility.hpp>
+#include <boost/mp11/algorithm.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <type_traits>
+
+using boost::mp11::mp_valid;
+using boost::mp11::mp_at;
+using boost::mp11::mp_size_t;
+using boost::mp11::mp_list;
+
+int main()
+{
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_at>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_at, void>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_at, void, void>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_at, void, void, void>));
+
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_at, void, mp_size_t<0>>));
+
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_at, mp_list<>, mp_size_t<0>>));
+
+    BOOST_TEST_TRAIT_TRUE((mp_valid<mp_at, mp_list<void>, mp_size_t<0>>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_at, mp_list<void>, mp_size_t<1>>));
+
+    BOOST_TEST_TRAIT_TRUE((mp_valid<mp_at, mp_list<void, void>, mp_size_t<0>>));
+    BOOST_TEST_TRAIT_TRUE((mp_valid<mp_at, mp_list<void, void>, mp_size_t<1>>));
+    BOOST_TEST_TRAIT_FALSE((mp_valid<mp_at, mp_list<void, void>, mp_size_t<2>>));
+
+    return boost::report_errors();
+}
diff --git a/test/mp_for_each.cpp b/test/mp_for_each.cpp
index 31ad7c5..542493b 100644
--- a/test/mp_for_each.cpp
+++ b/test/mp_for_each.cpp
@@ -14,8 +14,6 @@
 #include <boost/detail/workaround.hpp>
 #include <tuple>
 
-using boost::mp11::mp_identity;
-
 #if !defined( BOOST_NO_CXX14_CONSTEXPR )
 # define CONSTEXPR14 constexpr
 #else
@@ -26,9 +24,9 @@ struct F
 {
     int s;
 
-    CONSTEXPR14 void operator()( mp_identity<int> ) { s = s * 10 + 1; }
-    CONSTEXPR14 void operator()( mp_identity<short> ) { s = s * 10 + 2; }
-    CONSTEXPR14 void operator()( mp_identity<char> ) { s = s * 10 + 3; }
+    CONSTEXPR14 void operator()( int ) { s = s * 10 + 1; }
+    CONSTEXPR14 void operator()( short ) { s = s * 10 + 2; }
+    CONSTEXPR14 void operator()( char ) { s = s * 10 + 3; }
 };
 
 using boost::mp11::mp_list;