diff --git a/llvm/utils/TableGen/DFAEmitter.cpp b/llvm/utils/TableGen/DFAEmitter.cpp
--- a/llvm/utils/TableGen/DFAEmitter.cpp
+++ b/llvm/utils/TableGen/DFAEmitter.cpp
@@ -174,7 +174,7 @@
 struct Action {
   Record *R = nullptr;
   unsigned I = 0;
-  std::string S = nullptr;
+  std::string S;

   Action() = default;
   Action(Record *R, unsigned I, std::string S) : R(R), I(I), S(S) {}