diff --git a/include/llvm/Support/YAMLTraits.h b/include/llvm/Support/YAMLTraits.h
index 023dcee7d54..75253f1c83e 100644
--- a/include/llvm/Support/YAMLTraits.h
+++ b/include/llvm/Support/YAMLTraits.h
@@ -447,6 +447,7 @@ public:
 
   virtual void beginEnumScalar() = 0;
   virtual bool matchEnumScalar(const char*, bool) = 0;
+  virtual bool matchEnumFallback() = 0;
   virtual void endEnumScalar() = 0;
 
   virtual bool beginBitSetScalar(bool &) = 0;
@@ -472,6 +473,15 @@ public:
     }
   }
 
+  template <typename FBT, typename T>
+  void enumFallback(T &Val) {
+    if ( matchEnumFallback() ) {
+      FBT Res = Val;
+      yamlize(*this, Res, true);
+      Val = Res;
+    }
+  }
+
   template <typename T>
   void bitSetCase(T &Val, const char* Str, const T ConstVal) {
     if ( bitSetMatch(Str, outputting() && (Val & ConstVal) == ConstVal) ) {
@@ -899,6 +909,7 @@ private:
   void endFlowSequence() override;
   void beginEnumScalar() override;
   bool matchEnumScalar(const char*, bool) override;
+  bool matchEnumFallback() override;
   void endEnumScalar() override;
   bool beginBitSetScalar(bool &) override;
   bool bitSetMatch(const char *, bool ) override;
@@ -1026,6 +1037,7 @@ public:
   void endFlowSequence() override;
   void beginEnumScalar() override;
   bool matchEnumScalar(const char*, bool) override;
+  bool matchEnumFallback() override;
   void endEnumScalar() override;
   bool beginBitSetScalar(bool &) override;
   bool bitSetMatch(const char *, bool ) override;
diff --git a/lib/Support/YAMLTraits.cpp b/lib/Support/YAMLTraits.cpp
index c87790efb8c..fc23f31de33 100644
--- a/lib/Support/YAMLTraits.cpp
+++ b/lib/Support/YAMLTraits.cpp
@@ -233,6 +233,13 @@ bool Input::matchEnumScalar(const char *Str, bool) {
   return false;
 }
 
+bool Input::matchEnumFallback() {
+  if (ScalarMatchFound)
+    return false;
+  ScalarMatchFound = true;
+  return true;
+}
+
 void Input::endEnumScalar() {
   if (!ScalarMatchFound) {
     setError(CurrentNode, "unknown enumerated scalar");
@@ -508,6 +515,13 @@ bool Output::matchEnumScalar(const char *Str, bool Match) {
   return false;
 }
 
+bool Output::matchEnumFallback() {
+  if (EnumerationMatchFound)
+    return false;
+  EnumerationMatchFound = true;
+  return true;
+}
+
 void Output::endEnumScalar() {
   if (!EnumerationMatchFound)
     llvm_unreachable("bad runtime enum value");