diff --git a/MODULE.bazel b/MODULE.bazel
index 090309f2a..b013fb86e 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -64,9 +64,15 @@ bazel_dep(
 )
 bazel_dep(
     name = "cel-spec",
-    version = "0.25.1",
+    version = "0.25.2",
     repo_name = "com_google_cel_spec",
 )
+git_override(
+    module_name = "cel-spec",
+    commit = "ba58ae5007845f3a1279b488cdeb79645ce958bb",
+    remote = "https://github.com/cel-expr/cel-spec",
+)
+
 bazel_dep(
     name = "platforms",
     version = "1.1.0",
diff --git a/conformance/BUILD b/conformance/BUILD
index a5889f83b..b4ac3718f 100644
--- a/conformance/BUILD
+++ b/conformance/BUILD
@@ -47,6 +47,7 @@ cc_library(
         "//extensions:comprehensions_v2_functions",
         "//extensions:comprehensions_v2_macros",
         "//extensions:encoders",
+        "//extensions:lists_functions",
         "//extensions:math_ext",
         "//extensions:math_ext_decls",
         "//extensions:math_ext_macros",
@@ -143,6 +144,7 @@ _ALL_TESTS = [
     "@com_google_cel_spec//tests/simple:testdata/fp_math.textproto",
     "@com_google_cel_spec//tests/simple:testdata/integer_math.textproto",
     "@com_google_cel_spec//tests/simple:testdata/lists.textproto",
+    "@com_google_cel_spec//tests/simple:testdata/lists_ext.textproto",
     "@com_google_cel_spec//tests/simple:testdata/logic.textproto",
     "@com_google_cel_spec//tests/simple:testdata/macros.textproto",
     "@com_google_cel_spec//tests/simple:testdata/macros2.textproto",
@@ -228,6 +230,9 @@ _TESTS_TO_SKIP_LEGACY = _TESTS_TO_SKIP + [
     "block_ext/basic/optional_map",
     "block_ext/basic/optional_map_chained",
     "block_ext/basic/optional_message",
+
+    # lists_ext not implemented for legacy evaluator
+    "lists_ext",
 ]
 
 _TESTS_TO_SKIP_LEGACY_DASHBOARD = [
diff --git a/conformance/service.cc b/conformance/service.cc
index 8a456a9f4..c826d4572 100644
--- a/conformance/service.cc
+++ b/conformance/service.cc
@@ -60,6 +60,7 @@
 #include "extensions/comprehensions_v2_functions.h"
 #include "extensions/comprehensions_v2_macros.h"
 #include "extensions/encoders.h"
+#include "extensions/lists_functions.h"
 #include "extensions/math_ext.h"
 #include "extensions/math_ext_decls.h"
 #include "extensions/math_ext_macros.h"
@@ -147,6 +148,7 @@ absl::Status LegacyParse(const conformance::v1alpha1::ParseRequest& request,
   CEL_RETURN_IF_ERROR(cel::extensions::RegisterBindingsMacros(macros, options));
   CEL_RETURN_IF_ERROR(cel::extensions::RegisterMathMacros(macros, options));
   CEL_RETURN_IF_ERROR(cel::extensions::RegisterProtoMacros(macros, options));
+  CEL_RETURN_IF_ERROR(cel::extensions::RegisterListsMacros(macros, options));
   CEL_RETURN_IF_ERROR(cel::test::RegisterTestMacros(macros));
   CEL_ASSIGN_OR_RETURN(auto source, cel::NewSource(request.cel_source(),
                                                    request.source_location()));
@@ -192,6 +194,8 @@ absl::Status CheckImpl(google::protobuf::Arena* arena,
         builder->AddLibrary(cel::extensions::EncodersCheckerLibrary()));
     CEL_RETURN_IF_ERROR(
         builder->AddLibrary(cel::extensions::ComprehensionsV2CheckerLibrary()));
+    CEL_RETURN_IF_ERROR(
+        builder->AddLibrary(cel::extensions::ListsCheckerLibrary()));
   }
 
   for (const auto& decl : request.type_env()) {
@@ -201,7 +205,7 @@ absl::Status CheckImpl(google::protobuf::Arena* arena,
           auto fn_decl, cel::FunctionDeclFromV1Alpha1Proto(
                             name, decl.function(),
                             google::protobuf::DescriptorPool::generated_pool(), arena));
-      CEL_RETURN_IF_ERROR(builder->AddFunction(std::move(fn_decl)));
+      CEL_RETURN_IF_ERROR(builder->MergeFunction(std::move(fn_decl)));
     } else if (decl.has_ident()) {
       CEL_ASSIGN_OR_RETURN(
           auto var_decl, cel::VariableDeclFromV1Alpha1Proto(
@@ -536,6 +540,8 @@ class ModernConformanceServiceImpl : public ConformanceServiceInterface {
         builder.function_registry(), options));
     CEL_RETURN_IF_ERROR(cel::extensions::RegisterMathExtensionFunctions(
         builder.function_registry(), options));
+    CEL_RETURN_IF_ERROR(cel::extensions::RegisterListsFunctions(
+        builder.function_registry(), options));
 
     return std::move(builder).Build();
   }