diff --git a/fuzztest/internal/domains/protobuf_domain_impl.h b/fuzztest/internal/domains/protobuf_domain_impl.h
index 2e8b860..e452d96 100644
--- a/fuzztest/internal/domains/protobuf_domain_impl.h
+++ b/fuzztest/internal/domains/protobuf_domain_impl.h
@@ -1283,8 +1283,7 @@
     if constexpr (std::is_same_v<T, std::string>) {
       if (field->type() == FieldDescriptor::TYPE_STRING) {
         // Can only use UTF-8. For now, simplify as just ASCII.
-        return Domain<T>(ContainerOfImpl<std::string, InRangeImpl<char>>(
-            InRangeImpl<char>(char{0}, char{127})));
+        return Domain<T>(AsciiString());
       }
     }