diff --git a/rmw_zenoh_cpp/src/detail/liveliness_utils.cpp b/rmw_zenoh_cpp/src/detail/liveliness_utils.cpp
index a2aef62e..db93ec3f 100644
--- a/rmw_zenoh_cpp/src/detail/liveliness_utils.cpp
+++ b/rmw_zenoh_cpp/src/detail/liveliness_utils.cpp
@@ -192,7 +192,7 @@ std::optional<rmw_qos_profile_t> keyexpr_to_qos(const std::string & keyexpr)
   // Get the history depth.
   errno = 0;
   char * endptr;
-  int64_t num = strtol(history_parts[1].c_str(), &endptr, 10);
+  unsigned long num = strtoul(history_parts[1].c_str(), &endptr, 10);
   if (endptr == history_parts[1].c_str()) {
     // No values were converted, this is an error
     RMW_SET_ERROR_MSG("no valid numbers available");