diff --git a/src/common/serialization.h b/src/common/serialization.h
index e298efdf..c82c0def 100644
--- a/src/common/serialization.h
+++ b/src/common/serialization.h
@@ -606,7 +606,7 @@ struct std::hash<GroupRequest> {
  * from waiting indefinitely for the socket to be connected to.
  */
 struct GroupResponse {
-    int pid;
+    pid_t pid;
 
     template <typename S>
     void serialize(S& s) {