diff --git a/demo/main.cpp b/demo/main.cpp
index d0ac893..cfeddcc 100644
--- a/demo/main.cpp
+++ b/demo/main.cpp
@@ -18,7 +18,7 @@
 #include <string>
 
 struct author {
-    unsigned long id{};
+    unsigned int id{};
     std::string first_name;
     std::string last_name;
     std::string date_of_birth;
@@ -38,7 +38,7 @@ struct author {
 };
 
 struct book {
-    unsigned long id{};
+    unsigned int id{};
     matador::object::object_ptr<author> book_author;
     std::string title;
     unsigned short published_in{};
@@ -54,7 +54,7 @@ struct book {
 };
 
 struct payload {
-    unsigned long id{};
+    unsigned int id{};
 
     template<typename Operator>
     void process( Operator& op ) {
@@ -77,7 +77,7 @@ struct job {
         Background
     };
 
-    unsigned long id{};
+    unsigned int id{};
     matador::object::object_ptr<payload> payload;
     std::string type;
     std::string description;