diff --git a/include/clang/Basic/DiagnosticLexKinds.td b/include/clang/Basic/DiagnosticLexKinds.td
index 1652236..77db0a3 100644
--- a/include/clang/Basic/DiagnosticLexKinds.td
+++ b/include/clang/Basic/DiagnosticLexKinds.td
@@ -127,15 +127,16 @@
 def err_multichar_utf_character_literal : Error<
   "Unicode character literals may not contain multiple characters">;
 def err_exponent_has_no_digits : Error<"exponent has no digits">;
-def ext_imaginary_constant : Extension<"imaginary constants are an extension">;
+def ext_imaginary_constant : Extension<
+  "imaginary constants are a GNU extension">, InGroup<GNU>;
 def err_hexconstant_requires_exponent : Error<
   "hexadecimal floating constants require an exponent">;
 def err_hexconstant_requires_digits : Error<
   "hexadecimal floating constants require a significand">;
 def ext_hexconstant_invalid : Extension<
-  "hexadecimal floating constants are a C99 feature">;
+  "hexadecimal floating constants are a C99 feature">, InGroup<C99>;
 def ext_binary_literal : Extension<
-  "binary integer literals are an extension">;
+  "binary integer literals are a GNU extension">, InGroup<GNU>;
 def err_pascal_string_too_long : Error<"Pascal string is too long">;
 def warn_octal_escape_too_large : ExtWarn<"octal escape sequence out of range">;
 def warn_hex_escape_too_large : ExtWarn<"hex escape sequence out of range">;
diff --git a/include/clang/Basic/DiagnosticParseKinds.td b/include/clang/Basic/DiagnosticParseKinds.td
index 929835a..99932bc 100644
--- a/include/clang/Basic/DiagnosticParseKinds.td
+++ b/include/clang/Basic/DiagnosticParseKinds.td
@@ -50,7 +50,7 @@
 def ext_plain_complex : ExtWarn<
   "plain '_Complex' requires a type specifier; assuming '_Complex double'">;
 def ext_integer_complex : Extension<
-  "complex integer types are an extension">;
+  "complex integer types are a GNU extension">, InGroup<GNU>;
 def ext_thread_before : Extension<"'__thread' before '%0'">;
 
 def ext_empty_struct_union : Extension<
@@ -445,7 +445,8 @@
 def err_expected_lbrace_after_base_specifiers : Error<
   "expected '{' after base class list">;
 def ext_ellipsis_exception_spec : Extension<
-  "exception specification of '...' is a Microsoft extension">;
+  "exception specification of '...' is a Microsoft extension">,
+  InGroup<Microsoft>;
 def err_dynamic_and_noexcept_specification : Error<
   "cannot have both throw() and noexcept() clause on the same function">;
 def warn_cxx98_compat_noexcept_decl : Warning<
diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 97e49bb..ab5023f 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -95,7 +95,7 @@
 
 // C99 Designated Initializers
 def ext_designated_init : Extension<
-  "designated initializers are a C99 feature">;
+  "designated initializers are a C99 feature">, InGroup<C99>;
 def err_array_designator_negative : Error<
   "array designator value '%0' is negative">;
 def err_array_designator_empty_range : Error<
@@ -5047,7 +5047,9 @@
   "cast to incomplete type %0">;
 def ext_typecheck_cast_nonscalar : Extension<
   "C99 forbids casting nonscalar type %0 to the same type">;
-def ext_typecheck_cast_to_union : Extension<"C99 forbids casts to union type">;
+def ext_typecheck_cast_to_union : Extension<
+  "cast to union type is a GNU extension">,
+  InGroup<GNU>;
 def err_typecheck_cast_to_union_no_type : Error<
   "cast to union type from type %0 not present in union">;
 def err_cast_pointer_from_non_pointer_int : Error<
@@ -5214,7 +5216,7 @@
 
 def ext_in_class_initializer_non_constant : Extension<
   "in-class initializer for static data member is not a constant expression; "
-  "folding it to a constant is a GNU extension">;
+  "folding it to a constant is a GNU extension">, InGroup<GNU>;
 
 // C++ anonymous unions and GNU anonymous structs/unions
 def ext_anonymous_union : Extension<
diff --git a/test/Misc/warning-flags.c b/test/Misc/warning-flags.c
index c29f495..721bc3d 100644
--- a/test/Misc/warning-flags.c
+++ b/test/Misc/warning-flags.c
@@ -173,4 +173,4 @@
 
 The list of warnings in -Wpedantic should NEVER grow.
 
-CHECK: Number in -Wpedantic (not covered by other -W flags): 37
+CHECK: Number in -Wpedantic (not covered by other -W flags): 29
diff --git a/test/Sema/builtins.c b/test/Sema/builtins.c
index 357b7b6..e3b3b7e 100644
--- a/test/Sema/builtins.c
+++ b/test/Sema/builtins.c
@@ -40,7 +40,7 @@
 
   old = __sync_fetch_and_add();  // expected-error {{too few arguments to function call}}
   old = __sync_fetch_and_add(&old);  // expected-error {{too few arguments to function call}}
-  old = __sync_fetch_and_add((unsigned*)0, 42i); // expected-warning {{imaginary constants are an extension}}
+  old = __sync_fetch_and_add((unsigned*)0, 42i); // expected-warning {{imaginary constants are a GNU extension}}
 
   // PR7600: Pointers are implicitly casted to integers and back.
   void *old_ptr = __sync_val_compare_and_swap((void**)0, 0, 0);
diff --git a/test/Sema/cast-to-union.c b/test/Sema/cast-to-union.c
index c32964d..7b995e3 100644
--- a/test/Sema/cast-to-union.c
+++ b/test/Sema/cast-to-union.c
@@ -4,16 +4,16 @@
 void f(union u);
 
 void test(int x) {
-  f((union u)x); // expected-warning {{C99 forbids casts to union type}}
+  f((union u)x); // expected-warning {{cast to union type is a GNU extension}}
   f((union u)&x); // expected-error {{cast to union type from type 'int *' not present in union}}
   f((union u)2U); // expected-error {{cast to union type from type 'unsigned int' not present in union}}
 }
 
-union u w = (union u)2; // expected-warning {{C99 forbids casts to union type}}
+union u w = (union u)2; // expected-warning {{cast to union type is a GNU extension}}
 union u ww = (union u)1.0; // expected-error{{cast to union type from type 'double' not present in union}}
 union u x = 7; // expected-error{{initializing 'union u' with an expression of incompatible type 'int'}}
 int i;
-union u zz = (union u)i; // expected-error{{initializer element is not a compile-time constant}}  expected-warning {{C99 forbids casts to union type}}
+union u zz = (union u)i; // expected-error{{initializer element is not a compile-time constant}}  expected-warning {{cast to union type is a GNU extension}}
 
 struct s {int a, b;};
 struct s y = { 1, 5 };
diff --git a/test/Sema/exprs.c b/test/Sema/exprs.c
index a93e12e..df3e258 100644
--- a/test/Sema/exprs.c
+++ b/test/Sema/exprs.c
@@ -40,7 +40,7 @@
 }
 
 _Complex double test2() {
-  return 1.0if;    // expected-warning {{imaginary constants are an extension}}
+  return 1.0if;    // expected-warning {{imaginary constants are a GNU extension}}
 }
 
 // rdar://6097308