diff --git a/runtime/base/variant_map.h b/runtime/base/variant_map.h
index 8655a9e..1d7596a 100644
--- a/runtime/base/variant_map.h
+++ b/runtime/base/variant_map.h
@@ -31,7 +31,7 @@
 //
 // struct VariantMap {
 //   template <typename TValue>
-//   TValue* Get(Key<T> key);  // nullptr if the value was never set, otherwise the value.
+//   TValue* Get(Key<T> key);  // null if the value was never set, otherwise the value.
 //
 //   template <typename TValue>
 //   void Set(Key<T> key, TValue value);