Index: lib/Frontend/InitPreprocessor.cpp
===================================================================
--- lib/Frontend/InitPreprocessor.cpp
+++ lib/Frontend/InitPreprocessor.cpp
@@ -535,7 +535,7 @@
   if (LangOpts.ConceptsTS)
     Builder.defineMacro("__cpp_experimental_concepts", "1");
   if (LangOpts.CoroutinesTS)
-    Builder.defineMacro("__cpp_coroutines", "1");
+    Builder.defineMacro("__cpp_coroutines", "201703L");
 }
 
 static void InitializePredefinedMacros(const TargetInfo &TI,
Index: test/Lexer/cxx-features.cpp
===================================================================
--- test/Lexer/cxx-features.cpp
+++ test/Lexer/cxx-features.cpp
@@ -235,6 +235,6 @@
 #error "wrong value for __cpp_experimental_concepts"
 #endif
 
-#if (COROUTINES && !__cpp_coroutines) || (!COROUTINES && __cpp_coroutines)
+#if defined(COROUTINES) ? check(coroutines, 201703L, 201703L, 201703L, 201703L) : check(coroutines, 0, 0, 0, 0)
 #error "wrong value for __cpp_coroutines"
 #endif