diff --git a/compiler/compiler_factory_test.cc b/compiler/compiler_factory_test.cc
index 85c2711b7..9d6c663b3 100644
--- a/compiler/compiler_factory_test.cc
+++ b/compiler/compiler_factory_test.cc
@@ -49,7 +49,7 @@ TEST(CompilerFactoryTest, Works) {
       NewCompilerBuilder(cel::internal::GetSharedTestingDescriptorPool()));
 
   ASSERT_THAT(builder->AddLibrary(StandardCheckerLibrary()), IsOk());
-
+  builder->GetParserBuilder().GetOptions().enable_hidden_accumulator_var = true;
   ASSERT_OK_AND_ASSIGN(auto compiler, std::move(*builder).Build());
 
   ASSERT_OK_AND_ASSIGN(
@@ -71,18 +71,18 @@ TEST(CompilerFactoryTest, Works) {
       "c"~string
     ]~list(string),
     // Accumulator
-    __result__,
+    @result,
     // Init
     false~bool,
     // LoopCondition
     @not_strictly_false(
       !_(
-        __result__~bool^__result__
+        @result~bool^@result
       )~bool^logical_not
     )~bool^not_strictly_false,
     // LoopStep
     _||_(
-      __result__~bool^__result__,
+      @result~bool^@result,
       @in(
         x~string^x,
         [
@@ -93,7 +93,7 @@ TEST(CompilerFactoryTest, Works) {
       )~bool^in_list
     )~bool^logical_or,
     // Result
-    __result__~bool^__result__)~bool,
+    @result~bool^@result)~bool,
   _<_(
     10~int,
     _-_(
diff --git a/extensions/comprehensions_v2_macros.cc b/extensions/comprehensions_v2_macros.cc
index 04793ad39..a89b206cf 100644
--- a/extensions/comprehensions_v2_macros.cc
+++ b/extensions/comprehensions_v2_macros.cc
@@ -72,7 +72,7 @@ absl::optional<Expr> ExpandAllMacro2(MacroExprFactory& factory, Expr& target,
   auto result = factory.NewAccuIdent();
   return factory.NewComprehension(
       args[0].ident_expr().name(), args[1].ident_expr().name(),
-      std::move(target), kAccumulatorVariableName, std::move(init),
+      std::move(target), factory.AccuVarName(), std::move(init),
       std::move(condition), std::move(step), std::move(result));
 }
 
@@ -119,7 +119,7 @@ absl::optional<Expr> ExpandExistsMacro2(MacroExprFactory& factory, Expr& target,
   auto result = factory.NewAccuIdent();
   return factory.NewComprehension(
       args[0].ident_expr().name(), args[1].ident_expr().name(),
-      std::move(target), kAccumulatorVariableName, std::move(init),
+      std::move(target), factory.AccuVarName(), std::move(init),
       std::move(condition), std::move(step), std::move(result));
 }
 
@@ -172,7 +172,7 @@ absl::optional<Expr> ExpandExistsOneMacro2(MacroExprFactory& factory,
                                 factory.NewIntConst(1));
   return factory.NewComprehension(
       args[0].ident_expr().name(), args[1].ident_expr().name(),
-      std::move(target), kAccumulatorVariableName, std::move(init),
+      std::move(target), factory.AccuVarName(), std::move(init),
       std::move(condition), std::move(step), std::move(result));
 }
 
@@ -220,7 +220,7 @@ absl::optional<Expr> ExpandFilterMacro2(MacroExprFactory& factory, Expr& target,
   step = factory.NewCall(CelOperator::CONDITIONAL, std::move(args[2]),
                          std::move(step), factory.NewAccuIdent());
   return factory.NewComprehension(
-      name, name2, std::move(target), kAccumulatorVariableName, std::move(init),
+      name, name2, std::move(target), factory.AccuVarName(), std::move(init),
       std::move(condition), std::move(step), factory.NewAccuIdent());
 }
 
@@ -268,7 +268,7 @@ absl::optional<Expr> ExpandTransformList3Macro(MacroExprFactory& factory,
       CelOperator::ADD, factory.NewAccuIdent(),
       factory.NewList(factory.NewListElement(std::move(args[2]))));
   return factory.NewComprehension(std::move(iter_var), std::move(iter_var2),
-                                  std::move(target), kAccumulatorVariableName,
+                                  std::move(target), factory.AccuVarName(),
                                   factory.NewList(), factory.NewBoolConst(true),
                                   std::move(step), factory.NewAccuIdent());
 }
@@ -319,7 +319,7 @@ absl::optional<Expr> ExpandTransformList4Macro(MacroExprFactory& factory,
   step = factory.NewCall(CelOperator::CONDITIONAL, std::move(args[2]),
                          std::move(step), factory.NewAccuIdent());
   return factory.NewComprehension(std::move(iter_var), std::move(iter_var2),
-                                  std::move(target), kAccumulatorVariableName,
+                                  std::move(target), factory.AccuVarName(),
                                   factory.NewList(), factory.NewBoolConst(true),
                                   std::move(step), factory.NewAccuIdent());
 }
@@ -367,7 +367,7 @@ absl::optional<Expr> ExpandTransformMap3Macro(MacroExprFactory& factory,
   auto step = factory.NewCall("cel.@mapInsert", factory.NewAccuIdent(),
                               std::move(args[0]), std::move(args[2]));
   return factory.NewComprehension(std::move(iter_var), std::move(iter_var2),
-                                  std::move(target), kAccumulatorVariableName,
+                                  std::move(target), factory.AccuVarName(),
                                   factory.NewMap(), factory.NewBoolConst(true),
                                   std::move(step), factory.NewAccuIdent());
 }
@@ -417,7 +417,7 @@ absl::optional<Expr> ExpandTransformMap4Macro(MacroExprFactory& factory,
   step = factory.NewCall(CelOperator::CONDITIONAL, std::move(args[2]),
                          std::move(step), factory.NewAccuIdent());
   return factory.NewComprehension(std::move(iter_var), std::move(iter_var2),
-                                  std::move(target), kAccumulatorVariableName,
+                                  std::move(target), factory.AccuVarName(),
                                   factory.NewMap(), factory.NewBoolConst(true),
                                   std::move(step), factory.NewAccuIdent());
 }
diff --git a/parser/options.h b/parser/options.h
index 50f02a4bb..8e6d2ee3b 100644
--- a/parser/options.h
+++ b/parser/options.h
@@ -52,7 +52,7 @@ struct ParserOptions final {
   bool disable_standard_macros = false;
 
   // Enable hidden accumulator variable '@result' for builtin comprehensions.
-  bool enable_hidden_accumulator_var = false;
+  bool enable_hidden_accumulator_var = true;
 };
 
 }  // namespace cel
diff --git a/parser/parser_test.cc b/parser/parser_test.cc
index 1bf586bc8..1b5ff197a 100644
--- a/parser/parser_test.cc
+++ b/parser/parser_test.cc
@@ -458,7 +458,7 @@ std::vector<TestInfo> test_cases = {
      "  // Target\n"
      "  m^#1:Expr.Ident#,\n"
      "  // Accumulator\n"
-     "  __result__,\n"
+     "  @result,\n"
      "  // Init\n"
      "  0^#5:int64#,\n"
      "  // LoopCondition\n"
@@ -467,14 +467,14 @@ std::vector<TestInfo> test_cases = {
      "  _?_:_(\n"
      "    f^#4:Expr.Ident#,\n"
      "    _+_(\n"
-     "      __result__^#7:Expr.Ident#,\n"
+     "      @result^#7:Expr.Ident#,\n"
      "      1^#8:int64#\n"
      "    )^#9:Expr.Call#,\n"
-     "    __result__^#10:Expr.Ident#\n"
+     "    @result^#10:Expr.Ident#\n"
      "  )^#11:Expr.Call#,\n"
      "  // Result\n"
      "  _==_(\n"
-     "    __result__^#12:Expr.Ident#,\n"
+     "    @result^#12:Expr.Ident#,\n"
      "    1^#13:int64#\n"
      "  )^#14:Expr.Call#)^#15:Expr.Comprehension#",
      "", "", "",
@@ -489,20 +489,20 @@ std::vector<TestInfo> test_cases = {
      "  // Target\n"
      "  m^#1:Expr.Ident#,\n"
      "  // Accumulator\n"
-     "  __result__,\n"
+     "  @result,\n"
      "  // Init\n"
      "  []^#5:Expr.CreateList#,\n"
      "  // LoopCondition\n"
      "  true^#6:bool#,\n"
      "  // LoopStep\n"
      "  _+_(\n"
-     "    __result__^#7:Expr.Ident#,\n"
+     "    @result^#7:Expr.Ident#,\n"
      "    [\n"
      "      f^#4:Expr.Ident#\n"
      "    ]^#8:Expr.CreateList#\n"
      "  )^#9:Expr.Call#,\n"
      "  // Result\n"
-     "  __result__^#10:Expr.Ident#)^#11:Expr.Comprehension#",
+     "  @result^#10:Expr.Ident#)^#11:Expr.Comprehension#",
      "", "", "",
      "m^#1:Expr.Ident#.map(\n"
      "  v^#3:Expr.Ident#,\n"
@@ -515,7 +515,7 @@ std::vector<TestInfo> test_cases = {
      "  // Target\n"
      "  m^#1:Expr.Ident#,\n"
      "  // Accumulator\n"
-     "  __result__,\n"
+     "  @result,\n"
      "  // Init\n"
      "  []^#6:Expr.CreateList#,\n"
      "  // LoopCondition\n"
@@ -524,15 +524,15 @@ std::vector<TestInfo> test_cases = {
      "  _?_:_(\n"
      "    p^#4:Expr.Ident#,\n"
      "    _+_(\n"
-     "      __result__^#8:Expr.Ident#,\n"
+     "      @result^#8:Expr.Ident#,\n"
      "      [\n"
      "        f^#5:Expr.Ident#\n"
      "      ]^#9:Expr.CreateList#\n"
      "    )^#10:Expr.Call#,\n"
-     "    __result__^#11:Expr.Ident#\n"
+     "    @result^#11:Expr.Ident#\n"
      "  )^#12:Expr.Call#,\n"
      "  // Result\n"
-     "  __result__^#13:Expr.Ident#)^#14:Expr.Comprehension#",
+     "  @result^#13:Expr.Ident#)^#14:Expr.Comprehension#",
      "", "", "",
      "m^#1:Expr.Ident#.map(\n"
      "  v^#3:Expr.Ident#,\n"
@@ -546,7 +546,7 @@ std::vector<TestInfo> test_cases = {
      "  // Target\n"
      "  m^#1:Expr.Ident#,\n"
      "  // Accumulator\n"
-     "  __result__,\n"
+     "  @result,\n"
      "  // Init\n"
      "  []^#5:Expr.CreateList#,\n"
      "  // LoopCondition\n"
@@ -555,15 +555,15 @@ std::vector<TestInfo> test_cases = {
      "  _?_:_(\n"
      "    p^#4:Expr.Ident#,\n"
      "    _+_(\n"
-     "      __result__^#7:Expr.Ident#,\n"
+     "      @result^#7:Expr.Ident#,\n"
      "      [\n"
      "        v^#3:Expr.Ident#\n"
      "      ]^#8:Expr.CreateList#\n"
      "    )^#9:Expr.Call#,\n"
-     "    __result__^#10:Expr.Ident#\n"
+     "    @result^#10:Expr.Ident#\n"
      "  )^#11:Expr.Call#,\n"
      "  // Result\n"
-     "  __result__^#12:Expr.Ident#)^#13:Expr.Comprehension#",
+     "  @result^#12:Expr.Ident#)^#13:Expr.Comprehension#",
      "", "", "",
      "m^#1:Expr.Ident#.filter(\n"
      "  v^#3:Expr.Ident#,\n"
@@ -931,7 +931,7 @@ std::vector<TestInfo> test_cases = {
      "  // Target\n"
      "  x^#1:Expr.Ident#,\n"
      "  // Accumulator\n"
-     "  __result__,\n"
+     "  @result,\n"
      "  // Init\n"
      "  []^#19:Expr.CreateList#,\n"
      "  // LoopCondition\n"
@@ -944,7 +944,7 @@ std::vector<TestInfo> test_cases = {
      "      // Target\n"
      "      y^#4:Expr.Ident#,\n"
      "      // Accumulator\n"
-     "      __result__,\n"
+     "      @result,\n"
      "      // Init\n"
      "      []^#10:Expr.CreateList#,\n"
      "      // LoopCondition\n"
@@ -956,25 +956,25 @@ std::vector<TestInfo> test_cases = {
      "          0^#9:int64#\n"
      "        )^#8:Expr.Call#,\n"
      "        _+_(\n"
-     "          __result__^#12:Expr.Ident#,\n"
+     "          @result^#12:Expr.Ident#,\n"
      "          [\n"
      "            z^#6:Expr.Ident#\n"
      "          ]^#13:Expr.CreateList#\n"
      "        )^#14:Expr.Call#,\n"
-     "        __result__^#15:Expr.Ident#\n"
+     "        @result^#15:Expr.Ident#\n"
      "      )^#16:Expr.Call#,\n"
      "      // Result\n"
-     "      __result__^#17:Expr.Ident#)^#18:Expr.Comprehension#,\n"
+     "      @result^#17:Expr.Ident#)^#18:Expr.Comprehension#,\n"
      "    _+_(\n"
-     "      __result__^#21:Expr.Ident#,\n"
+     "      @result^#21:Expr.Ident#,\n"
      "      [\n"
      "        y^#3:Expr.Ident#\n"
      "      ]^#22:Expr.CreateList#\n"
      "    )^#23:Expr.Call#,\n"
-     "    __result__^#24:Expr.Ident#\n"
+     "    @result^#24:Expr.Ident#\n"
      "  )^#25:Expr.Call#,\n"
      "  // Result\n"
-     "  __result__^#26:Expr.Ident#)^#27:Expr.Comprehension#"
+     "  @result^#26:Expr.Ident#)^#27:Expr.Comprehension#"
      "",
      "", "", "",
      "x^#1:Expr.Ident#.filter(\n"
@@ -995,7 +995,7 @@ std::vector<TestInfo> test_cases = {
      "  // Target\n"
      "  a^#2:Expr.Ident#.b~test-only~^#4:Expr.Select#,\n"
      "  // Accumulator\n"
-     "  __result__,\n"
+     "  @result,\n"
      "  // Init\n"
      "  []^#8:Expr.CreateList#,\n"
      "  // LoopCondition\n"
@@ -1004,15 +1004,15 @@ std::vector<TestInfo> test_cases = {
      "  _?_:_(\n"
      "    c^#7:Expr.Ident#,\n"
      "    _+_(\n"
-     "      __result__^#10:Expr.Ident#,\n"
+     "      @result^#10:Expr.Ident#,\n"
      "      [\n"
      "        c^#6:Expr.Ident#\n"
      "      ]^#11:Expr.CreateList#\n"
      "    )^#12:Expr.Call#,\n"
-     "    __result__^#13:Expr.Ident#\n"
+     "    @result^#13:Expr.Ident#\n"
      "  )^#14:Expr.Call#,\n"
      "  // Result\n"
-     "  __result__^#15:Expr.Ident#)^#16:Expr.Comprehension#",
+     "  @result^#15:Expr.Ident#)^#16:Expr.Comprehension#",
      "", "", "",
      "^#4:has#.filter(\n"
      "  c^#6:Expr.Ident#,\n"
@@ -1028,7 +1028,7 @@ std::vector<TestInfo> test_cases = {
      "  // Target\n"
      "  x^#1:Expr.Ident#,\n"
      "  // Accumulator\n"
-     "  __result__,\n"
+     "  @result,\n"
      "  // Init\n"
      "  []^#35:Expr.CreateList#,\n"
      "  // LoopCondition\n"
@@ -1042,55 +1042,55 @@ std::vector<TestInfo> test_cases = {
      "        // Target\n"
      "        y^#4:Expr.Ident#,\n"
      "        // Accumulator\n"
-     "        __result__,\n"
+     "        @result,\n"
      "        // Init\n"
      "        false^#11:bool#,\n"
      "        // LoopCondition\n"
      "        @not_strictly_false(\n"
      "          !_(\n"
-     "            __result__^#12:Expr.Ident#\n"
+     "            @result^#12:Expr.Ident#\n"
      "          )^#13:Expr.Call#\n"
      "        )^#14:Expr.Call#,\n"
      "        // LoopStep\n"
      "        _||_(\n"
-     "          __result__^#15:Expr.Ident#,\n"
+     "          @result^#15:Expr.Ident#,\n"
      "          z^#8:Expr.Ident#.a~test-only~^#10:Expr.Select#\n"
      "        )^#16:Expr.Call#,\n"
      "        // Result\n"
-     "        __result__^#17:Expr.Ident#)^#18:Expr.Comprehension#,\n"
+     "        @result^#17:Expr.Ident#)^#18:Expr.Comprehension#,\n"
      "      __comprehension__(\n"
      "        // Variable\n"
      "        z,\n"
      "        // Target\n"
      "        y^#19:Expr.Ident#,\n"
      "        // Accumulator\n"
-     "        __result__,\n"
+     "        @result,\n"
      "        // Init\n"
      "        false^#26:bool#,\n"
      "        // LoopCondition\n"
      "        @not_strictly_false(\n"
      "          !_(\n"
-     "            __result__^#27:Expr.Ident#\n"
+     "            @result^#27:Expr.Ident#\n"
      "          )^#28:Expr.Call#\n"
      "        )^#29:Expr.Call#,\n"
      "        // LoopStep\n"
      "        _||_(\n"
-     "          __result__^#30:Expr.Ident#,\n"
+     "          @result^#30:Expr.Ident#,\n"
      "          z^#23:Expr.Ident#.b~test-only~^#25:Expr.Select#\n"
      "        )^#31:Expr.Call#,\n"
      "        // Result\n"
-     "        __result__^#32:Expr.Ident#)^#33:Expr.Comprehension#\n"
+     "        @result^#32:Expr.Ident#)^#33:Expr.Comprehension#\n"
      "    )^#34:Expr.Call#,\n"
      "    _+_(\n"
-     "      __result__^#37:Expr.Ident#,\n"
+     "      @result^#37:Expr.Ident#,\n"
      "      [\n"
      "        y^#3:Expr.Ident#\n"
      "      ]^#38:Expr.CreateList#\n"
      "    )^#39:Expr.Call#,\n"
-     "    __result__^#40:Expr.Ident#\n"
+     "    @result^#40:Expr.Ident#\n"
      "  )^#41:Expr.Call#,\n"
      "  // Result\n"
-     "  __result__^#42:Expr.Ident#)^#43:Expr.Comprehension#",
+     "  @result^#42:Expr.Ident#)^#43:Expr.Comprehension#",
      "", "", "",
      "x^#1:Expr.Ident#.filter(\n"
      "  y^#3:Expr.Ident#,\n"
@@ -1121,22 +1121,22 @@ std::vector<TestInfo> test_cases = {
      "  // Target\n"
      "  a^#2:Expr.Ident#.b~test-only~^#4:Expr.Select#.asList()^#5:Expr.Call#,\n"
      "  // Accumulator\n"
-     "  __result__,\n"
+     "  @result,\n"
      "  // Init\n"
      "  false^#9:bool#,\n"
      "  // LoopCondition\n"
      "  @not_strictly_false(\n"
      "    !_(\n"
-     "      __result__^#10:Expr.Ident#\n"
+     "      @result^#10:Expr.Ident#\n"
      "    )^#11:Expr.Call#\n"
      "  )^#12:Expr.Call#,\n"
      "  // LoopStep\n"
      "  _||_(\n"
-     "    __result__^#13:Expr.Ident#,\n"
+     "    @result^#13:Expr.Ident#,\n"
      "    c^#8:Expr.Ident#\n"
      "  )^#14:Expr.Call#,\n"
      "  // Result\n"
-     "  __result__^#15:Expr.Ident#)^#16:Expr.Comprehension#",
+     "  @result^#15:Expr.Ident#)^#16:Expr.Comprehension#",
      "", "", "",
      "^#4:has#.asList()^#5:Expr.Call#.exists(\n"
      "  c^#7:Expr.Ident#,\n"
@@ -1155,22 +1155,22 @@ std::vector<TestInfo> test_cases = {
      "    c^#7:Expr.Ident#.d~test-only~^#9:Expr.Select#\n"
      "  ]^#1:Expr.CreateList#,\n"
      "  // Accumulator\n"
-     "  __result__,\n"
+     "  @result,\n"
      "  // Init\n"
      "  false^#13:bool#,\n"
      "  // LoopCondition\n"
      "  @not_strictly_false(\n"
      "    !_(\n"
-     "      __result__^#14:Expr.Ident#\n"
+     "      @result^#14:Expr.Ident#\n"
      "    )^#15:Expr.Call#\n"
      "  )^#16:Expr.Call#,\n"
      "  // LoopStep\n"
      "  _||_(\n"
-     "    __result__^#17:Expr.Ident#,\n"
+     "    @result^#17:Expr.Ident#,\n"
      "    e^#12:Expr.Ident#\n"
      "  )^#18:Expr.Call#,\n"
      "  // Result\n"
-     "  __result__^#19:Expr.Ident#)^#20:Expr.Comprehension#",
+     "  @result^#19:Expr.Ident#)^#20:Expr.Comprehension#",
      "", "", "",
      "[\n"
      "  ^#5:has#,\n"
@@ -1401,6 +1401,7 @@ class ExpressionTest : public testing::TestWithParam<TestInfo> {};
 TEST_P(ExpressionTest, Parse) {
   const TestInfo& test_info = GetParam();
   ParserOptions options;
+  options.enable_hidden_accumulator_var = true;
   if (!test_info.M.empty()) {
     options.add_macro_calls = true;
   }
@@ -1549,25 +1550,25 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "  // Target\n"
        "  []^#1:Expr.CreateList#,\n"
        "  // Accumulator\n"
-       "  @result,\n"
+       "  __result__,\n"
        "  // Init\n"
        "  false^#7:bool#,\n"
        "  // LoopCondition\n"
        "  @not_strictly_false(\n"
        "    !_(\n"
-       "      @result^#8:Expr.Ident#\n"
+       "      __result__^#8:Expr.Ident#\n"
        "    )^#9:Expr.Call#\n"
        "  )^#10:Expr.Call#,\n"
        "  // LoopStep\n"
        "  _||_(\n"
-       "    @result^#11:Expr.Ident#,\n"
+       "    __result__^#11:Expr.Ident#,\n"
        "    _>_(\n"
        "      x^#4:Expr.Ident#,\n"
        "      0^#6:int64#\n"
        "    )^#5:Expr.Call#\n"
        "  )^#12:Expr.Call#,\n"
        "  // Result\n"
-       "  @result^#13:Expr.Ident#)^#14:Expr.Comprehension#"},
+       "  __result__^#13:Expr.Ident#)^#14:Expr.Comprehension#"},
       {"[].exists_one(x, x > 0)",
        "__comprehension__(\n"
        "  // Variable\n"
@@ -1575,7 +1576,7 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "  // Target\n"
        "  []^#1:Expr.CreateList#,\n"
        "  // Accumulator\n"
-       "  @result,\n"
+       "  __result__,\n"
        "  // Init\n"
        "  0^#7:int64#,\n"
        "  // LoopCondition\n"
@@ -1587,14 +1588,14 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "      0^#6:int64#\n"
        "    )^#5:Expr.Call#,\n"
        "    _+_(\n"
-       "      @result^#9:Expr.Ident#,\n"
+       "      __result__^#9:Expr.Ident#,\n"
        "      1^#10:int64#\n"
        "    )^#11:Expr.Call#,\n"
-       "    @result^#12:Expr.Ident#\n"
+       "    __result__^#12:Expr.Ident#\n"
        "  )^#13:Expr.Call#,\n"
        "  // Result\n"
        "  _==_(\n"
-       "    @result^#14:Expr.Ident#,\n"
+       "    __result__^#14:Expr.Ident#,\n"
        "    1^#15:int64#\n"
        "  )^#16:Expr.Call#)^#17:Expr.Comprehension#"},
       {"[].all(x, x > 0)",
@@ -1604,23 +1605,23 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "  // Target\n"
        "  []^#1:Expr.CreateList#,\n"
        "  // Accumulator\n"
-       "  @result,\n"
+       "  __result__,\n"
        "  // Init\n"
        "  true^#7:bool#,\n"
        "  // LoopCondition\n"
        "  @not_strictly_false(\n"
-       "    @result^#8:Expr.Ident#\n"
+       "    __result__^#8:Expr.Ident#\n"
        "  )^#9:Expr.Call#,\n"
        "  // LoopStep\n"
        "  _&&_(\n"
-       "    @result^#10:Expr.Ident#,\n"
+       "    __result__^#10:Expr.Ident#,\n"
        "    _>_(\n"
        "      x^#4:Expr.Ident#,\n"
        "      0^#6:int64#\n"
        "    )^#5:Expr.Call#\n"
        "  )^#11:Expr.Call#,\n"
        "  // Result\n"
-       "  @result^#12:Expr.Ident#)^#13:Expr.Comprehension#"},
+       "  __result__^#12:Expr.Ident#)^#13:Expr.Comprehension#"},
       {"[].map(x, x + 1)",
        "__comprehension__(\n"
        "  // Variable\n"
@@ -1628,14 +1629,14 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "  // Target\n"
        "  []^#1:Expr.CreateList#,\n"
        "  // Accumulator\n"
-       "  @result,\n"
+       "  __result__,\n"
        "  // Init\n"
        "  []^#7:Expr.CreateList#,\n"
        "  // LoopCondition\n"
        "  true^#8:bool#,\n"
        "  // LoopStep\n"
        "  _+_(\n"
-       "    @result^#9:Expr.Ident#,\n"
+       "    __result__^#9:Expr.Ident#,\n"
        "    [\n"
        "      _+_(\n"
        "        x^#4:Expr.Ident#,\n"
@@ -1644,7 +1645,7 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "    ]^#10:Expr.CreateList#\n"
        "  )^#11:Expr.Call#,\n"
        "  // Result\n"
-       "  @result^#12:Expr.Ident#)^#13:Expr.Comprehension#"},
+       "  __result__^#12:Expr.Ident#)^#13:Expr.Comprehension#"},
       {"[].map(x, x > 0, x + 1)",
        "__comprehension__(\n"
        "  // Variable\n"
@@ -1652,7 +1653,7 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "  // Target\n"
        "  []^#1:Expr.CreateList#,\n"
        "  // Accumulator\n"
-       "  @result,\n"
+       "  __result__,\n"
        "  // Init\n"
        "  []^#10:Expr.CreateList#,\n"
        "  // LoopCondition\n"
@@ -1664,7 +1665,7 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "      0^#6:int64#\n"
        "    )^#5:Expr.Call#,\n"
        "    _+_(\n"
-       "      @result^#12:Expr.Ident#,\n"
+       "      __result__^#12:Expr.Ident#,\n"
        "      [\n"
        "        _+_(\n"
        "          x^#7:Expr.Ident#,\n"
@@ -1672,10 +1673,10 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "        )^#8:Expr.Call#\n"
        "      ]^#13:Expr.CreateList#\n"
        "    )^#14:Expr.Call#,\n"
-       "    @result^#15:Expr.Ident#\n"
+       "    __result__^#15:Expr.Ident#\n"
        "  )^#16:Expr.Call#,\n"
        "  // Result\n"
-       "  @result^#17:Expr.Ident#)^#18:Expr.Comprehension#"},
+       "  __result__^#17:Expr.Ident#)^#18:Expr.Comprehension#"},
       {"[].filter(x, x > 0)",
        "__comprehension__(\n"
        "  // Variable\n"
@@ -1683,7 +1684,7 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "  // Target\n"
        "  []^#1:Expr.CreateList#,\n"
        "  // Accumulator\n"
-       "  @result,\n"
+       "  __result__,\n"
        "  // Init\n"
        "  []^#7:Expr.CreateList#,\n"
        "  // LoopCondition\n"
@@ -1695,15 +1696,15 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
        "      0^#6:int64#\n"
        "    )^#5:Expr.Call#,\n"
        "    _+_(\n"
-       "      @result^#9:Expr.Ident#,\n"
+       "      __result__^#9:Expr.Ident#,\n"
        "      [\n"
        "        x^#3:Expr.Ident#\n"
        "      ]^#10:Expr.CreateList#\n"
        "    )^#11:Expr.Call#,\n"
-       "    @result^#12:Expr.Ident#\n"
+       "    __result__^#12:Expr.Ident#\n"
        "  )^#13:Expr.Call#,\n"
        "  // Result\n"
-       "  @result^#14:Expr.Ident#)^#15:Expr.Comprehension#"},
+       "  __result__^#14:Expr.Ident#)^#15:Expr.Comprehension#"},
       // Maintain restriction on '__result__' variable name until the default is
       // changed everywhere.
       {
@@ -1758,12 +1759,12 @@ const std::vector<TestInfo>& UpdatedAccuVarTestCases() {
   return *kInstance;
 }
 
-class UpdatedAccuVarTest : public testing::TestWithParam<TestInfo> {};
+class UpdatedAccuVarDisabledTest : public testing::TestWithParam<TestInfo> {};
 
-TEST_P(UpdatedAccuVarTest, Parse) {
+TEST_P(UpdatedAccuVarDisabledTest, Parse) {
   const TestInfo& test_info = GetParam();
   ParserOptions options;
-  options.enable_hidden_accumulator_var = true;
+  options.enable_hidden_accumulator_var = false;
   if (!test_info.M.empty()) {
     options.add_macro_calls = true;
   }
@@ -1864,7 +1865,7 @@ std::string TestName(const testing::TestParamInfo<TestInfo>& test_info) {
 INSTANTIATE_TEST_SUITE_P(CelParserTest, ExpressionTest,
                          testing::ValuesIn(test_cases), TestName);
 
-INSTANTIATE_TEST_SUITE_P(UpdatedAccuVarTest, UpdatedAccuVarTest,
+INSTANTIATE_TEST_SUITE_P(UpdatedAccuVarTest, UpdatedAccuVarDisabledTest,
                          testing::ValuesIn(UpdatedAccuVarTestCases()),
                          TestName);
 
diff --git a/testutil/expr_printer_test.cc b/testutil/expr_printer_test.cc
index d15699d5a..9b1e7ca37 100644
--- a/testutil/expr_printer_test.cc
+++ b/testutil/expr_printer_test.cc
@@ -238,7 +238,7 @@ TEST(ExprPrinterTest, Comprehension) {
   Expr expr;
   expr.set_id(1);
   expr.mutable_comprehension_expr().set_iter_var("x");
-  expr.mutable_comprehension_expr().set_accu_var("__result__");
+  expr.mutable_comprehension_expr().set_accu_var("@result");
   auto& range = expr.mutable_comprehension_expr().mutable_iter_range();
   range.set_id(2);
   range.mutable_ident_expr().set_name("range");
@@ -263,7 +263,7 @@ TEST(ExprPrinterTest, Comprehension) {
   // Target
   range#2,
   // Accumulator
-  __result__,
+  @result,
   // Init
   accu_init#3,
   // LoopCondition
@@ -277,6 +277,7 @@ TEST(ExprPrinterTest, Comprehension) {
 TEST(ExprPrinterTest, Proto) {
   ParserOptions options;
   options.enable_optional_syntax = true;
+  options.enable_hidden_accumulator_var = true;
   ASSERT_OK_AND_ASSIGN(auto parsed_expr, Parse(R"cel(
     "foo".startsWith("bar") ||
     [1, ?2, 3].exists(x, x in {?"b": "foo"}) ||
@@ -306,18 +307,18 @@ TEST(ExprPrinterTest, Proto) {
         3#7
       ]#4,
       // Accumulator
-      __result__,
+      @result,
       // Init
       false#16,
       // LoopCondition
       @not_strictly_false(
         !_(
-          __result__#17
+          @result#17
         )#18
       )#19,
       // LoopStep
       _||_(
-        __result__#20,
+        @result#20,
         @in(
           x#10,
           {
@@ -326,7 +327,7 @@ TEST(ExprPrinterTest, Proto) {
         )#11
       )#21,
       // Result
-      __result__#22)#23
+      @result#22)#23
   )#24,
   Foo{
     byte_value:b"bytes"#27#26,