Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -12101,7 +12101,7 @@
 
   StringRef LiteralName
     = FnDecl->getDeclName().getCXXLiteralIdentifier()->getName();
-  if (LiteralName[0] != '_') {
+  if (LiteralName[0] != '_' && !FnDecl->isInStdNamespace()) {
     // C++11 [usrlit.suffix]p1:
     //   Literal suffix identifiers that do not start with an underscore
     //   are reserved for future standardization.
Index: test/CXX/lex/lex.literal/lex.ext/p10.cpp
===================================================================
--- test/CXX/lex/lex.literal/lex.ext/p10.cpp
+++ test/CXX/lex/lex.literal/lex.ext/p10.cpp
@@ -12,3 +12,7 @@
   const char *p = ""wibble; // expected-error {{invalid suffix on literal; C++11 requires a space between literal and identifier}} expected-error {{expected ';'}}
   const char *q = R"x("hello")x"wibble; // expected-error {{invalid suffix on literal; C++11 requires a space between literal and identifier}} expected-error {{expected ';'}}
 }
+
+namespace std {
+  void operator "" stdwibble(const char*);
+}