1 files changed, 2 insertions, 2 deletions
diff --git a/lib/Expr/ExprBuilder.cpp b/lib/Expr/ExprBuilder.cpp
index e1cfa2d2..f8f57d35 100644
--- a/lib/Expr/ExprBuilder.cpp
+++ b/lib/Expr/ExprBuilder.cpp
@@ -326,8 +326,8 @@ namespace {
     virtual ref<Expr> Read(const UpdateList &Updates,
                            const ref<Expr> &Index) {
       // Roll back through writes when possible.
-      const UpdateNode *UN = Updates.head;
-      while (UN && Eq(Index, UN->index)->isFalse())
+      auto UN = Updates.head;
+      while (!UN.isNull() && Eq(Index, UN->index)->isFalse())
         UN = UN->next;
 
       if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Index))