diff --git a/onnxscript/_internal/ast_utils.py b/onnxscript/_internal/ast_utils.py
index c7250e1268..4146f38e2f 100644
--- a/onnxscript/_internal/ast_utils.py
+++ b/onnxscript/_internal/ast_utils.py
@@ -6,12 +6,9 @@
 
 import ast
 import inspect
-import sys
 import textwrap
 from typing import Callable
 
-PY_VERSION_GE_39 = sys.version_info >= (3, 9)
-
 
 def get_src_and_ast(func: Callable, /) -> tuple[str, ast.FunctionDef]:
     try:
@@ -35,17 +32,10 @@ def normalize_subscript_expr(expr: ast.Subscript):
     # Returns a list of expressions, denoting the indices, after stripping the extraneous "Index"
     # wrapper present in python versions before 3.9
     index_expr = expr.slice
-    if PY_VERSION_GE_39:
-        if isinstance(index_expr, ast.Tuple):
-            return index_expr.elts  # multiple indices
-        else:
-            return [index_expr]  # single index
+    if isinstance(index_expr, ast.Tuple):
+        return index_expr.elts  # multiple indices
     else:
-        if isinstance(index_expr, ast.ExtSlice):
-            indices = index_expr.dims  # type: ignore[attr-defined]
-        else:
-            indices = [index_expr]  # single slice-index
-        return [x.value if isinstance(x, ast.Index) else x for x in indices]  # type: ignore[attr-defined]
+        return [index_expr]  # single index
 
 
 def is_print_call(stmt: ast.stmt) -> bool:
diff --git a/onnxscript/converter.py b/onnxscript/converter.py
index 2d10a73764..1ee6e0ecd0 100644
--- a/onnxscript/converter.py
+++ b/onnxscript/converter.py
@@ -23,9 +23,6 @@
 from onnxscript import type_annotation as ta
 from onnxscript._internal import analysis, ast_utils, autocast, param_manipulation
 
-PY_VERSION_GE_39 = ast_utils.PY_VERSION_GE_39
-
-
 logger = logging.getLogger("onnxscript")
 
 
@@ -435,14 +432,10 @@ def _is_constant_expr(self, node: ast.AST) -> None:
                 ast.BinOp,
                 ast.UnaryOp,
                 ast.Compare,
-                ast.Num,
-                ast.Str,
                 ast.Attribute,
                 ast.List,
                 ast.Load,
-                ast.NameConstant,
                 ast.Constant,
-                ast.Str,
             ),
         ):
             return all(self._is_constant_expr(c) for c in ast.iter_child_nodes(node))
@@ -578,9 +571,9 @@ def _translate_expr(
 
     def _translate_opt_expr(self, node: ast.expr) -> Optional[Variable]:
         """Translation of an expression where "None" is permitted (eg., for an optional argument).
-        None is represented as a NameConstant in Python 3.7 and Constant in Python 3.9.
+        None is represented as a Constant in Python 3.9+.
         """
-        if isinstance(node, (ast.NameConstant, ast.Constant)) and (node.value is None):
+        if isinstance(node, ast.Constant) and (node.value is None):
             return None
         return self._translate_expr(node)
 
@@ -629,7 +622,7 @@ def _translate_subscript_expr(
             target = f"{var_name}_subscripted"
         target = self.generate_unique_name(target)
         indices = ast_utils.normalize_subscript_expr(node)
-        info = self._source_of(node.slice if PY_VERSION_GE_39 else node)
+        info = self._source_of(node.slice)
 
         # Create cached int constants:
         # TODO: Do this at a graph-scope level.
diff --git a/onnxscript/converter_test.py b/onnxscript/converter_test.py
index 46d88f9f12..6305bddf70 100644
--- a/onnxscript/converter_test.py
+++ b/onnxscript/converter_test.py
@@ -5,7 +5,6 @@
 import inspect
 import os
 import pathlib
-import sys
 import textwrap
 import types
 import typing
@@ -437,8 +436,7 @@ def f1(A: FLOAT[...]) -> FLOAT[...]:
             r = A[index]
             return r
 
-        ast_name = "_ast" if sys.version_info[:2] < (3, 9) else "ast"
-        self.check_failure(f1, f"Left term must be a tuple not '<class '{ast_name}.Name'>'")
+        self.check_failure(f1, "Left term must be a tuple not '<class 'ast.Name'>'")
 
     def check_run(self, onnxfn, inputs, expected_output):
         # Test by converting to model and running with ORT