diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
index c5647fbc22a3..34b8ab0b47f2 100644
--- a/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -134,6 +134,7 @@ static const Value *getUnderlyingObjectForInstr(const MachineInstr *MI,
 }
 
 void ScheduleDAGInstrs::StartBlock(MachineBasicBlock *BB) {
+  LoopRegs.Deps.clear();
   if (MachineLoop *ML = MLI.getLoopFor(BB))
     if (BB == ML->getLoopLatch()) {
       MachineBasicBlock *Header = ML->getHeader();
diff --git a/llvm/lib/CodeGen/ScheduleDAGInstrs.h b/llvm/lib/CodeGen/ScheduleDAGInstrs.h
index 6e672f4b7272..666bdf548c71 100644
--- a/llvm/lib/CodeGen/ScheduleDAGInstrs.h
+++ b/llvm/lib/CodeGen/ScheduleDAGInstrs.h
@@ -48,7 +48,8 @@ namespace llvm {
     /// VisitLoop - Clear out any previous state and analyze the given loop.
     ///
     void VisitLoop(const MachineLoop *Loop) {
-      Deps.clear();
+      assert(Deps.empty() && "stale loop dependencies");
+
       MachineBasicBlock *Header = Loop->getHeader();
       SmallSet<unsigned, 8> LoopLiveIns;
       for (MachineBasicBlock::livein_iterator LI = Header->livein_begin(),