diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
index 95cee824c40b77..f50bcd8ea90bb8 100644
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -1171,6 +1171,7 @@ Parser::isCXXDeclarationSpecifier(ImplicitTypenameContext AllowImplicitTypename,
   case tok::kw_inline:
   case tok::kw_virtual:
   case tok::kw_explicit:
+  case tok::kw__Noreturn:
 
     // Modules
   case tok::kw___module_private__:
@@ -1225,6 +1226,7 @@ Parser::isCXXDeclarationSpecifier(ImplicitTypenameContext AllowImplicitTypename,
     // GNU
   case tok::kw_restrict:
   case tok::kw__Complex:
+  case tok::kw__Imaginary:
   case tok::kw___attribute:
   case tok::kw___auto_type:
     return TPResult::True;
diff --git a/clang/test/Interpreter/disambiguate-decl-stmt.cpp b/clang/test/Interpreter/disambiguate-decl-stmt.cpp
index 1f4d5e267288bc..f2a59c510f9a27 100644
--- a/clang/test/Interpreter/disambiguate-decl-stmt.cpp
+++ b/clang/test/Interpreter/disambiguate-decl-stmt.cpp
@@ -102,3 +102,16 @@ __attribute((noreturn)) Attrs2::Attrs2() = default;
 
 // Extra semicolon
 namespace N {};
+
+// Test C keywords supported in all language modes.
+// https://clang.llvm.org/docs/LanguageExtensions.html#c-keywords-supported-in-all-language-modes
+
+_Alignas(16) int aligned_var;
+int align = _Alignof(double);
+_Atomic int atomic_var = 0;
+_Complex double complex_val = 1.0 + 2.0i;
+_Float16 f = 1.5;
+_Thread_local int counter = 0;
+_Static_assert(sizeof(int) == 4, "int must be 4 bytes");
+_Imaginary float i = 2.0f; // expected-error {{imaginary types are not supported}}
+_Noreturn void noreturn_func() { while (true) {} }
\ No newline at end of file