diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 5124376a98a..fa5c5b894c8 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -272,7 +272,7 @@ BasicAliasAnalysis::getModRefInfo(CallSite CS, Value *P, unsigned Size) {
       // If this is a tail call and P points to a stack location, we know that
       // the tail call cannot access or modify the local stack.
       if (isa<AllocaInst>(Object) ||
-          cast<Argument>(Object)->hasByValAttr())
+          (isa<Argument>(Object) && cast<Argument>(Object)->hasByValAttr()))
         if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
           if (CI->isTailCall())
             return NoModRef;