Index: clang/lib/Lex/PPMacroExpansion.cpp
===================================================================
--- clang/lib/Lex/PPMacroExpansion.cpp
+++ clang/lib/Lex/PPMacroExpansion.cpp
@@ -1813,7 +1813,11 @@
 
     if (!Tok.isAnnotation() && Tok.getIdentifierInfo())
       Tok.setKind(tok::identifier);
-    else {
+    else if (Tok.is(tok::string_literal)) {
+      const StringRef StrData(Tok.getLiteralData() + 1, Tok.getLength() - 2);
+      Tok.setIdentifierInfo(this->getIdentifierInfo(StrData));
+      Tok.setKind(tok::identifier);
+    } else {
       Diag(Tok.getLocation(), diag::err_pp_identifier_arg_not_identifier)
         << Tok.getKind();
       // Don't walk past anything that's not a real token.
Index: clang/test/Parser/MicrosoftExtensions.cpp
===================================================================
--- clang/test/Parser/MicrosoftExtensions.cpp
+++ clang/test/Parser/MicrosoftExtensions.cpp
@@ -270,8 +270,10 @@
   // FIXME: We should pick a friendlier display name for this token kind.
   __identifier(1) // expected-error {{cannot convert <numeric_constant> token to an identifier}}
   __identifier(+) // expected-error {{cannot convert '+' token to an identifier}}
-  __identifier("foo") // expected-error {{cannot convert <string_literal> token to an identifier}}
   __identifier(;) // expected-error {{cannot convert ';' token to an identifier}}
+  __identifier("1"); // expected-error {{use of undeclared identifier '1'}}
+  __identifier("+"); // expected-error {{use of undeclared identifier '+'}}
+  __identifier(";"); // expected-error {{use of undeclared identifier ';'}}
 }
 
 class inline_definition_pure_spec {