diff --git a/src/libravatarserv.hpp b/src/libravatarserv.hpp
index 4144e60..477f93e 100644
--- a/src/libravatarserv.hpp
+++ b/src/libravatarserv.hpp
@@ -48,7 +48,7 @@ namespace http  // http.cpp
     struct Request
     {
         const string digest;
-        uint16_t size;
+        const uint16_t size;
         const string fallback;
     };