Index: include/__config
===================================================================
--- include/__config
+++ include/__config
@@ -687,7 +687,7 @@
 #define _NOALIAS
 #endif
 
-#if __has_feature(cxx_explicit_conversions) || defined(__IBMCPP__)
+#if __has_feature(cxx_explicit_conversions) || defined(__IBMCPP__) || _GNUC_VER >= 406
 #   define _LIBCPP_EXPLICIT explicit
 #else
 #   define _LIBCPP_EXPLICIT
Index: test/std/diagnostics/syserr/syserr.errcode/syserr.errcode.observers/bool.fail.cpp
===================================================================
--- test/std/diagnostics/syserr/syserr.errcode/syserr.errcode.observers/bool.fail.cpp
+++ test/std/diagnostics/syserr/syserr.errcode/syserr.errcode.observers/bool.fail.cpp
@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <system_error>
+
+// class error_code
+
+// explicit operator bool() const;
+
+#include <system_error>
+
+int main()
+{
+    const std::error_code ec(0, std::generic_category());
+    return ec;
+}
+