diff --git a/rmw_cyclonedds_cpp/src/serdata.cpp b/rmw_cyclonedds_cpp/src/serdata.cpp
index db3f78330d..c6d9b5f4ee 100644
--- a/rmw_cyclonedds_cpp/src/serdata.cpp
+++ b/rmw_cyclonedds_cpp/src/serdata.cpp
@@ -465,8 +465,10 @@ bool sertopic_rmw_equal(
 uint32_t sertopic_rmw_hash(const struct ddsi_sertopic * tpcmn)
 {
   const struct sertopic_rmw * tp = static_cast<const struct sertopic_rmw *>(tpcmn);
-  uint32_t h2 = std::hash<bool>{} (tp->is_request_header);
-  uint32_t h1 = std::hash<std::string>{} (std::string(tp->type_support.typesupport_identifier_));
+  uint32_t h2 = static_cast<uint32_t>(std::hash<bool>{} (tp->is_request_header));
+  uint32_t h1 =
+    static_cast<uint32_t>(std::hash<std::string>{} (std::string(
+      tp->type_support.typesupport_identifier_)));
   return h1 ^ h2;
 }
 #endif