diff --git a/include/llvm/CodeGen/MachineInstr.h b/include/llvm/CodeGen/MachineInstr.h
index ddaca4dae27..dac1c47c961 100644
--- a/include/llvm/CodeGen/MachineInstr.h
+++ b/include/llvm/CodeGen/MachineInstr.h
@@ -17,6 +17,7 @@
 #define LLVM_CODEGEN_MACHINEINSTR_H
 
 #include "Support/iterator"
+#include <string>
 #include <vector>
 #include <cassert>