diff --git a/eval/eval/attribute_utility.cc b/eval/eval/attribute_utility.cc
index 117516caf..1e044627e 100644
--- a/eval/eval/attribute_utility.cc
+++ b/eval/eval/attribute_utility.cc
@@ -123,7 +123,7 @@ absl::optional<UnknownValue> AttributeUtility::MergeUnknowns(
   }
 
   if (!result_set.has_value()) {
-    return absl::nullopt;
+    return std::nullopt;
   }
 
   return UnknownValue(cel::Unknown(result_set->unknown_attributes(),
diff --git a/eval/eval/container_access_step.cc b/eval/eval/container_access_step.cc
index fda51e34f..4cf4ebf4d 100644
--- a/eval/eval/container_access_step.cc
+++ b/eval/eval/container_access_step.cc
@@ -55,7 +55,7 @@ absl::optional<Number> CelNumberFromValue(const Value& value) {
     case ValueKind::kDouble:
       return Number::FromDouble(value.GetDouble().NativeValue());
     default:
-      return absl::nullopt;
+      return std::nullopt;
   }
 }
 
diff --git a/eval/eval/function_step.cc b/eval/eval/function_step.cc
index fcf429378..12c5af8a7 100644
--- a/eval/eval/function_step.cc
+++ b/eval/eval/function_step.cc
@@ -291,7 +291,7 @@ absl::StatusOr<ResolveResult> ResolveStatic(
       return overload;
     }
   }
-  return absl::nullopt;
+  return std::nullopt;
 }
 
 absl::StatusOr<ResolveResult> ResolveLazy(
@@ -299,7 +299,7 @@ absl::StatusOr<ResolveResult> ResolveLazy(
     bool receiver_style,
     absl::Span<const cel::FunctionRegistry::LazyOverload> providers,
     const ExecutionFrameBase& frame) {
-  ResolveResult result = absl::nullopt;
+  ResolveResult result = std::nullopt;
 
   std::vector<cel::Kind> arg_types(input_args.size());
 
diff --git a/eval/eval/select_step.cc b/eval/eval/select_step.cc
index 420f3ac31..b815f5d87 100644
--- a/eval/eval/select_step.cc
+++ b/eval/eval/select_step.cc
@@ -72,7 +72,7 @@ absl::optional<Value> CheckForMarkedAttributes(const AttributeTrail& trail,
     return cel::ErrorValue(std::move(result).status());
   }
 
-  return absl::nullopt;
+  return std::nullopt;
 }
 
 void TestOnlySelect(const StructValue& msg, const std::string& field,