diff --git a/include/mp/type-optional.h b/include/mp/type-optional.h
index 8bb74c4..80a8f4f 100644
--- a/include/mp/type-optional.h
+++ b/include/mp/type-optional.h
@@ -17,8 +17,7 @@ void CustomBuildField(TypeList<std::optional<LocalType>>,
 {
     if (value) {
         output.setHas();
-        // FIXME: should std::move value if destvalue is rref?
-        BuildField(TypeList<LocalType>(), invoke_context, output, *value);
+        BuildField(TypeList<LocalType>(), invoke_context, output, *std::forward<Value>(value));
     }
 }