Index: lib/Sema/SemaCoroutine.cpp
===================================================================
--- lib/Sema/SemaCoroutine.cpp
+++ lib/Sema/SemaCoroutine.cpp
@@ -444,6 +444,9 @@
     else {
       // non-class prvalues always have cv-unqualified types
       QualType AdjRetType = RetType.getUnqualifiedType();
+      if (auto *AT = dyn_cast<AutoType>(AdjRetType))
+        AdjRetType = AT->desugar();
+
       if (RetType->isReferenceType() ||
           (AdjRetType != S.Context.BoolTy && AdjRetType != S.Context.VoidTy)) {
         S.Diag(AwaitSuspend->getCalleeDecl()->getLocation(),
Index: test/SemaCXX/coroutines.cpp
===================================================================
--- test/SemaCXX/coroutines.cpp
+++ test/SemaCXX/coroutines.cpp
@@ -66,6 +66,12 @@
   void await_resume() {}
 };
 
+struct auto_await_suspend {
+  bool await_ready();
+  template <typename F> auto await_suspend(F) {}
+  void await_resume();
+};
+
 struct DummyVoidTag {};
 DummyVoidTag no_specialization() { // expected-error {{this function cannot be a coroutine: 'std::experimental::coroutine_traits<DummyVoidTag>' has no member named 'promise_type'}}
   co_await a;
@@ -159,6 +165,10 @@
   co_yield yield; // expected-error {{no member named 'await_ready' in 'not_awaitable'}}
 }
 
+void check_auto_await_suspend() {
+  co_await auto_await_suspend{}; // OK
+}
+
 void coreturn(int n) {
   co_await a;
   if (n == 0)