diff --git a/lib/CodeGen/RegAllocLinearScan.cpp b/lib/CodeGen/RegAllocLinearScan.cpp
index 919b94c..1e7d0a8 100644
--- a/lib/CodeGen/RegAllocLinearScan.cpp
+++ b/lib/CodeGen/RegAllocLinearScan.cpp
@@ -29,6 +29,7 @@
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/ADT/EquivalenceClasses.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Support/Debug.h"