diff --git a/eval/public/containers/container_backed_map_impl.cc b/eval/public/containers/container_backed_map_impl.cc
index 5ac08af92..d94bf6c5d 100644
--- a/eval/public/containers/container_backed_map_impl.cc
+++ b/eval/public/containers/container_backed_map_impl.cc
@@ -85,7 +85,7 @@ class CelValueEq {
 }  // namespace
 
 // Map element access operator.
-absl::optional<CelValue> CelMapBuilder::operator[](CelValue cel_key) const {
+std::optional<CelValue> CelMapBuilder::operator[](CelValue cel_key) const {
   auto item = values_map_.find(cel_key);
   if (item == values_map_.end()) {
     return absl::nullopt;
diff --git a/eval/public/containers/internal_field_backed_map_impl.cc b/eval/public/containers/internal_field_backed_map_impl.cc
index a879955d1..e62ef63ee 100644
--- a/eval/public/containers/internal_field_backed_map_impl.cc
+++ b/eval/public/containers/internal_field_backed_map_impl.cc
@@ -145,7 +145,7 @@ absl::StatusOr<bool> FieldBackedMapImpl::Has(const CelValue& key) const {
   return LookupMapValue(key, &value_ref);
 }
 
-absl::optional<CelValue> FieldBackedMapImpl::operator[](CelValue key) const {
+std::optional<CelValue> FieldBackedMapImpl::operator[](CelValue key) const {
   // Fast implementation which uses a friend method to do a hash-based key
   // lookup.
   MapValueConstRef value_ref;
@@ -236,7 +236,7 @@ absl::StatusOr<bool> FieldBackedMapImpl::LegacyHasMapValue(
   return true;
 }
 
-absl::optional<CelValue> FieldBackedMapImpl::LegacyLookupMapValue(
+std::optional<CelValue> FieldBackedMapImpl::LegacyLookupMapValue(
     const CelValue& key) const {
   // Ensure that the key matches the key type.
   if (!MatchesMapKeyType(key_desc_, key)) {