diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index d3b2e9a..a227f25 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -698,7 +698,7 @@
   if (getOpcode() == TargetInstrInfo::INLINEASM) {
     assert(DefOpIdx >= 2);
     const MachineOperand &MO = getOperand(DefOpIdx);
-    if (!MO.isReg() || !MO.isDef())
+    if (!MO.isReg() || !MO.isDef() || MO.getReg() == 0)
       return false;
     // Determine the actual operand no corresponding to this index.
     unsigned DefNo = 0;