diff --git a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
index e091928609f1..5699217157b7 100644
--- a/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
+++ b/llvm/lib/Transforms/Coroutines/CoroSplit.cpp
@@ -141,6 +141,7 @@ private:
     case Kind::SwitchCleanup:
       return true;
     }
+    llvm_unreachable("Unknown CoroCloner::Kind enum");
   }
 
   void createDeclaration();