diff --git a/lib/CodeGen/RegAllocPBQP.cpp b/lib/CodeGen/RegAllocPBQP.cpp
index e9271ef..1f49199 100644
--- a/lib/CodeGen/RegAllocPBQP.cpp
+++ b/lib/CodeGen/RegAllocPBQP.cpp
@@ -731,7 +731,7 @@
   typedef LiveInterval::Ranges::const_iterator LRIterator;
 
   // First allocate registers for the empty intervals.
-  for (LiveIntervalSet::iterator
+  for (LiveIntervalSet::const_iterator
 	 itr = emptyVRegIntervals.begin(), end = emptyVRegIntervals.end();
          itr != end; ++itr) {
     LiveInterval *li = *itr;