diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 38e77f0d1aca..4d784d5694ac 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -1804,6 +1804,8 @@ public:
           return "610";
         case CudaArch::SM_62:
           return "620";
+         default:
+           llvm_unreachable("unhandled CudaArch");
         }
       }();
       Builder.defineMacro("__CUDA_ARCH__", CUDAArchCode);