diff --git a/lib/CodeGen/MachineRegisterInfo.cpp b/lib/CodeGen/MachineRegisterInfo.cpp
index a777f52cb24..1af00e84a6e 100644
--- a/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/lib/CodeGen/MachineRegisterInfo.cpp
@@ -37,6 +37,7 @@ MachineRegisterInfo::~MachineRegisterInfo() {
 ///
 void
 MachineRegisterInfo::setRegClass(unsigned Reg, const TargetRegisterClass *RC) {
+  assert(RC && RC->isAllocatable() && "Invalid RC for virtual register");
   VRegInfo[Reg].first = RC;
 }