diff --git a/lib/CodeGen/MachineSSAUpdater.cpp b/lib/CodeGen/MachineSSAUpdater.cpp
index 99fb99a..84d6df2 100644
--- a/lib/CodeGen/MachineSSAUpdater.cpp
+++ b/lib/CodeGen/MachineSSAUpdater.cpp
@@ -329,7 +329,7 @@
   /// InstrIsPHI - Check if an instruction is a PHI.
   ///
   static MachineInstr *InstrIsPHI(MachineInstr *I) {
-    if (I->isPHI())
+    if (I && I->isPHI())
       return I;
     return 0;
   }