diff --git a/include/clang/AST/Builtins.def b/include/clang/AST/Builtins.def
index de755f5..7bdcd6d 100644
--- a/include/clang/AST/Builtins.def
+++ b/include/clang/AST/Builtins.def
@@ -99,6 +99,7 @@
 BUILTIN(__builtin_va_start, "va&.", "n")
 BUILTIN(__builtin_va_end, "va&", "n")
 BUILTIN(__builtin_va_copy, "va&a", "n")
+BUILTIN(__builtin_stdarg_start, "va&a", "n")
 BUILTIN(__builtin_memcpy, "v*v*vC*z", "n")
 BUILTIN(__builtin_return_address, "v*Ui", "n")
 BUILTIN(__builtin_frame_address, "v*Ui", "n")
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 8b98cba..183d9a9 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -205,7 +205,8 @@
 
   if (BID == Builtin::BI__builtin_va_start ||
       BID == Builtin::BI__builtin_va_copy ||
-      BID == Builtin::BI__builtin_va_end)
+      BID == Builtin::BI__builtin_va_end ||
+      BID == Builtin::BI__builtin_stdarg_start)
     InitBuiltinVaListType();
     
   QualType R = Context.BuiltinInfo.GetBuiltinType(BID, Context);