diff --git a/loopy/transform/buffer.py b/loopy/transform/buffer.py
index b494c52e3f979026699f0aa2e7ef74efb476d735..dd54fc12c20492a62b88b769d7a0ccefded7f7a4 100644
--- a/loopy/transform/buffer.py
+++ b/loopy/transform/buffer.py
@@ -75,7 +75,7 @@ class ArrayAccessReplacer(RuleAwareIdentityMapper):
                 expn_state.kernel,
                 expn_state.instruction,
                 expn_state.stack):
-            result = self.map_array_access(expr.index, expn_state)
+            result = self.map_array_access(expr.index_tuple, expn_state)
 
         if result is None:
             return super(ArrayAccessReplacer, self).map_subscript(expr, expn_state)