diff --git a/pyteal/ast/abi/type.py b/pyteal/ast/abi/type.py
index da3dc5bbc..b7ebe5bd5 100644
--- a/pyteal/ast/abi/type.py
+++ b/pyteal/ast/abi/type.py
@@ -90,7 +90,10 @@ def __init__(self, spec: TypeSpec) -> None:
             assert proto.mem_layout
             local_types = proto.mem_layout.local_stack_types
 
-            if len(local_types) < 128:
+            # NOTE: you can have at most 128 local variables.
+            # len(local_types) + 1 computes the resulting length,
+            # should be <= 128
+            if len(local_types) + 1 <= 128:
                 local_types.append(self._type_spec.storage_type())
                 self._stored_value = FrameVar(proto, len(local_types) - 1)
                 return