diff --git a/extensions/regex_functions.cc b/extensions/regex_functions.cc
index 912fa6511..3872e6217 100644
--- a/extensions/regex_functions.cc
+++ b/extensions/regex_functions.cc
@@ -119,13 +119,14 @@ CelValue CaptureStringN(Arena* arena, CelValue::StringHolder target,
   std::vector<std::pair<CelValue, CelValue>> cel_values;
   for (int index = 1; index <= capturing_groups_count; index++) {
     auto it = named_capturing_groups_map.find(index);
-    std::string name = it != named_capturing_groups_map.end()
-                           ? it->second
-                           : std::to_string(index);
+    CelValue name =
+        it != named_capturing_groups_map.end()
+            ? CelValue::CreateString(
+                  google::protobuf::Arena::Create<std::string>(arena, it->second))
+            : CelValue::CreateInt64(index);
     cel_values.emplace_back(
-        CelValue::CreateString(google::protobuf::Arena::Create<std::string>(arena, name)),
-        CelValue::CreateString(google::protobuf::Arena::Create<std::string>(
-            arena, captured_strings[index - 1])));
+        name, CelValue::CreateString(google::protobuf::Arena::Create<std::string>(
+                  arena, captured_strings[index - 1])));
   }
   auto container_map = google::api::expr::runtime::CreateContainerBackedMap(
       absl::MakeSpan(cel_values));
diff --git a/extensions/regex_functions_test.cc b/extensions/regex_functions_test.cc
index 50f02d6ba..9aef8f91c 100644
--- a/extensions/regex_functions_test.cc
+++ b/extensions/regex_functions_test.cc
@@ -77,10 +77,10 @@ class RegexFunctionsTest : public ::testing::TestWithParam<TestCase> {
 TEST_F(RegexFunctionsTest, CaptureStringSuccessWithCombinationOfGroups) {
   // combination of named and unnamed groups should return a celmap
   std::vector<std::pair<CelValue, CelValue>> cel_values;
-  cel_values.emplace_back(std::make_pair(
-      CelValue::CreateString(google::protobuf::Arena::Create<std::string>(&arena_, "1")),
-      CelValue::CreateString(
-          google::protobuf::Arena::Create<std::string>(&arena_, "user"))));
+  cel_values.emplace_back(
+      std::make_pair(CelValue::CreateInt64(1),
+                     CelValue::CreateString(
+                         google::protobuf::Arena::Create<std::string>(&arena_, "user"))));
   cel_values.emplace_back(std::make_pair(
       CelValue::CreateString(
           google::protobuf::Arena::Create<std::string>(&arena_, "Username")),
@@ -131,14 +131,14 @@ TEST_F(RegexFunctionsTest, CaptureStringSuccessWithSingleNamedGroup) {
 TEST_F(RegexFunctionsTest, CaptureStringSuccessWithMultipleUnamedGroups) {
   // Regex containing all unnamed groups should return a map
   std::vector<std::pair<CelValue, CelValue>> cel_values;
-  cel_values.emplace_back(std::make_pair(
-      CelValue::CreateString(google::protobuf::Arena::Create<std::string>(&arena_, "1")),
-      CelValue::CreateString(
-          google::protobuf::Arena::Create<std::string>(&arena_, "testuser"))));
-  cel_values.emplace_back(std::make_pair(
-      CelValue::CreateString(google::protobuf::Arena::Create<std::string>(&arena_, "2")),
-      CelValue::CreateString(
-          google::protobuf::Arena::Create<std::string>(&arena_, "testdomain"))));
+  cel_values.emplace_back(
+      std::make_pair(CelValue::CreateInt64(1),
+                     CelValue::CreateString(google::protobuf::Arena::Create<std::string>(
+                         &arena_, "testuser"))));
+  cel_values.emplace_back(
+      std::make_pair(CelValue::CreateInt64(2),
+                     CelValue::CreateString(google::protobuf::Arena::Create<std::string>(
+                         &arena_, "testdomain"))));
   auto container_map = google::api::expr::runtime::CreateContainerBackedMap(
       absl::MakeSpan(cel_values));
   // Release ownership of container_map to Arena.