Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -50,6 +50,7 @@
 def Coroutine : DiagGroup<"coroutine", [CoroutineMissingUnhandledException]>;
 def ConstantConversion :
   DiagGroup<"constant-conversion", [ BitFieldConstantConversion ] >;
+def CTAD : DiagGroup<"ctad">;
 def LiteralConversion : DiagGroup<"literal-conversion">;
 def StringConversion : DiagGroup<"string-conversion">;
 def SignConversion : DiagGroup<"sign-conversion">;
@@ -183,7 +184,8 @@
 def CXXPre14CompatPedantic : DiagGroup<"c++98-c++11-compat-pedantic",
                                        [CXXPre14Compat,
                                         CXXPre14CompatBinaryLiteral]>;
-def CXXPre17Compat : DiagGroup<"c++98-c++11-c++14-compat">;
+def CXXPre17Compat : DiagGroup<"c++98-c++11-c++14-compat",
+                                       [CTAD]>;
 def CXXPre17CompatPedantic : DiagGroup<"c++98-c++11-c++14-compat-pedantic",
                                        [CXXPre17Compat]>;
 def CXXPre2aCompat : DiagGroup<"c++98-c++11-c++14-c++17-compat">;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -2164,7 +2164,7 @@
 def warn_cxx14_compat_class_template_argument_deduction : Warning<
   "class template argument deduction is incompatible with C++ standards "
   "before C++17%select{|; for compatibility, use explicit type name %1}0">,
-  InGroup<CXXPre17Compat>, DefaultIgnore;
+  InGroup<CTAD>, DefaultIgnore;
 
 // C++14 deduced return types
 def err_auto_fn_deduction_failure : Error<