diff --git a/lib/Analysis/GRSimpleVals.cpp b/lib/Analysis/GRSimpleVals.cpp
index a2a59f3..48b25a7 100644
--- a/lib/Analysis/GRSimpleVals.cpp
+++ b/lib/Analysis/GRSimpleVals.cpp
@@ -369,7 +369,7 @@
 
     SVal V = StateMgr.GetSVal(St, *I);
     
-    if (isa<Loc>(V))
+    if (isa<loc::MemRegionVal>(V))
       St = StateMgr.SetSVal(St, cast<Loc>(V), UnknownVal());
     else if (isa<nonloc::LocAsInteger>(V))
       St = StateMgr.SetSVal(St, cast<nonloc::LocAsInteger>(V).getLoc(),