diff --git a/lib/CodeGen/MachineRegisterInfo.cpp b/lib/CodeGen/MachineRegisterInfo.cpp
index 34518fa..95d7a7d 100644
--- a/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/lib/CodeGen/MachineRegisterInfo.cpp
@@ -305,8 +305,6 @@
 #endif
 
 void MachineRegisterInfo::freezeReservedRegs(const MachineFunction &MF) {
-  assert (!reservedRegsFrozen() &&
-          "freezeReservedRegs should only be called once!");
   ReservedRegs = TRI->getReservedRegs(MF);
   assert(ReservedRegs.size() == TRI->getNumRegs() &&
          "Invalid ReservedRegs vector from target");
diff --git a/lib/CodeGen/RegAllocBase.cpp b/lib/CodeGen/RegAllocBase.cpp
index 2b598e3..993dbc7 100644
--- a/lib/CodeGen/RegAllocBase.cpp
+++ b/lib/CodeGen/RegAllocBase.cpp
@@ -58,6 +58,7 @@
   VRM = &vrm;
   LIS = &lis;
   Matrix = &mat;
+  MRI->freezeReservedRegs(vrm.getMachineFunction());
   RegClassInfo.runOnMachineFunction(vrm.getMachineFunction());
 }
 
diff --git a/lib/CodeGen/RegAllocFast.cpp b/lib/CodeGen/RegAllocFast.cpp
index 3744b06..8892216 100644
--- a/lib/CodeGen/RegAllocFast.cpp
+++ b/lib/CodeGen/RegAllocFast.cpp
@@ -1127,6 +1127,7 @@
   TM = &Fn.getTarget();
   TRI = TM->getRegisterInfo();
   TII = TM->getInstrInfo();
+  MRI->freezeReservedRegs(Fn);
   RegClassInfo.runOnMachineFunction(Fn);
   UsedInInstr.clear();
   UsedInInstr.setUniverse(TRI->getNumRegs());
diff --git a/lib/CodeGen/RegAllocPBQP.cpp b/lib/CodeGen/RegAllocPBQP.cpp
index f58d45f..02ebce7 100644
--- a/lib/CodeGen/RegAllocPBQP.cpp
+++ b/lib/CodeGen/RegAllocPBQP.cpp
@@ -552,6 +552,8 @@
   vrm = &getAnalysis<VirtRegMap>();
   spiller.reset(createInlineSpiller(*this, MF, *vrm));
 
+  mri->freezeReservedRegs(MF);
+
   DEBUG(dbgs() << "PBQP Register Allocating for " << mf->getName() << "\n");
 
   // Allocator main loop: