diff --git a/llvm/lib/Support/YAMLTraits.cpp b/llvm/lib/Support/YAMLTraits.cpp
--- a/llvm/lib/Support/YAMLTraits.cpp
+++ b/llvm/lib/Support/YAMLTraits.cpp
@@ -629,7 +629,7 @@
   outputUpToEndOfLine(" ]");
 }
 
-bool Output::preflightFlowElement(unsigned, void *&) {
+bool Output::preflightFlowElement(unsigned, void *&SaveInfo) {
   if (NeedFlowSequenceComma)
     output(", ");
   if (WrapColumn && Column > WrapColumn) {
@@ -639,6 +639,7 @@
     Column = ColumnAtFlowStart;
     output("  ");
   }
+  SaveInfo = nullptr;
   return true;
 }