diff --git a/include/boost/detail/container_fwd.hpp b/include/boost/detail/container_fwd.hpp
index 659e428..7df7ccb 100644
--- a/include/boost/detail/container_fwd.hpp
+++ b/include/boost/detail/container_fwd.hpp
@@ -38,7 +38,11 @@
 #    define BOOST_DETAIL_NO_CONTAINER_FWD
 #  elif defined(__GLIBCPP__) || defined(__GLIBCXX__)
      // GNU libstdc++ 3
-#    if defined(_GLIBCXX_DEBUG) \
+     //
+     // Disable forwarding for all recent versions, as the library has a
+     // versioned namespace mode, and I don't know how to detect it.
+#    if __GLIBCXX__ >= 20070513 \
+        || defined(_GLIBCXX_DEBUG) \
         || defined(_GLIBCXX_PARALLEL) \
         || defined(_GLIBCXX_PROFILE)
 #      define BOOST_DETAIL_NO_CONTAINER_FWD
diff --git a/include/boost/detail/fenv.hpp b/include/boost/detail/fenv.hpp
index 1ba8833..f048706 100644
--- a/include/boost/detail/fenv.hpp
+++ b/include/boost/detail/fenv.hpp
@@ -16,9 +16,10 @@
 
 /* If we're using clang + glibc, we have to get hacky. 
  * See http://llvm.org/bugs/show_bug.cgi?id=6907 */
-#if defined(__clang__)       &&                       \
+#if defined(__clang__)       &&  (__clang_major__ < 3) &&    \
     defined(__GNU_LIBRARY__) && /* up to version 5 */ \
-    defined(__GLIBC__)          /* version 6 + */
+    defined(__GLIBC__) &&         /* version 6 + */ \
+    !defined(_FENV_H)
   #define _FENV_H
 
   #include <features.h>