diff --git a/lib/Transforms/Scalar/LoopUnswitch.cpp b/lib/Transforms/Scalar/LoopUnswitch.cpp
index b6c6e03609d..f57b7bb5194 100644
--- a/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -112,8 +112,9 @@ namespace {
       AU.addPreserved<LoopInfo>();
       AU.addRequiredID(LCSSAID);
       AU.addPreservedID(LCSSAID);
-      AU.addPreserved<DominatorTree>();
-      AU.addPreserved<DominanceFrontier>();
+      // FIXME: Loop Unswitch does not preserve dominator info in all cases.
+      // AU.addPreserved<DominatorTree>();
+      // AU.addPreserved<DominanceFrontier>();
     }
 
   private: