diff --git a/clang/utils/TableGen/RISCVVEmitter.cpp b/clang/utils/TableGen/RISCVVEmitter.cpp
--- a/clang/utils/TableGen/RISCVVEmitter.cpp
+++ b/clang/utils/TableGen/RISCVVEmitter.cpp
@@ -297,7 +297,7 @@
   }
   // Illegal vscale result would be less than 1
   if (Log2ScaleResult < 0)
-    return None;
+    return llvm::None;
   return 1 << Log2ScaleResult;
 }