diff --git a/llvm/include/llvm/CodeGen/MachineInstrBuilder.h b/llvm/include/llvm/CodeGen/MachineInstrBuilder.h
index c6a6679c1b69..73611fe7db1e 100644
--- a/llvm/include/llvm/CodeGen/MachineInstrBuilder.h
+++ b/llvm/include/llvm/CodeGen/MachineInstrBuilder.h
@@ -39,6 +39,7 @@ namespace RegState {
 class MachineInstrBuilder {
   MachineInstr *MI;
 public:
+  MachineInstrBuilder() : MI(0) {}
   explicit MachineInstrBuilder(MachineInstr *mi) : MI(mi) {}
 
   /// Allow automatic conversion to the machine instruction we are working on.