diff --git a/include/clang/Basic/DiagnosticGroups.td b/include/clang/Basic/DiagnosticGroups.td
index 63afc63..c34bdc1 100644
--- a/include/clang/Basic/DiagnosticGroups.td
+++ b/include/clang/Basic/DiagnosticGroups.td
@@ -70,6 +70,9 @@
 def : DiagGroup<"shorten-64-to-32">;
 def : DiagGroup<"sign-compare">;
 
+// Preprocessor warnings.
+def : DiagGroup<"builtin-macro-redefined">;
+
 // Just silence warnings about common forms of -Wstrict-aliasing for now.
 def : DiagGroup<"strict-aliasing=0">;
 def : DiagGroup<"strict-aliasing=1">;
diff --git a/include/clang/Basic/DiagnosticLexKinds.td b/include/clang/Basic/DiagnosticLexKinds.td
index 9eda7bd..3f132c0 100644
--- a/include/clang/Basic/DiagnosticLexKinds.td
+++ b/include/clang/Basic/DiagnosticLexKinds.td
@@ -112,7 +112,8 @@
 def pp_out_of_date_dependency : Warning<
   "current file is older than dependency %0">;
 def pp_undef_builtin_macro : Warning<"undefining builtin macro">;
-def pp_redef_builtin_macro : Warning<"redefining builtin macro">;
+def pp_redef_builtin_macro : Warning<"redefining builtin macro">,
+  InGroup<DiagGroup<"builtin-macro-redefined">>;
 def pp_macro_not_used : Warning<"macro is not used">, DefaultIgnore,
   InGroup<DiagGroup<"unused-macros">>;
 def warn_pp_undef_identifier : Warning<