diff --git a/src/mesy_nng.h b/src/mesy_nng.h
index 8f5ed95..05db625 100644
--- a/src/mesy_nng.h
+++ b/src/mesy_nng.h
@@ -204,7 +204,8 @@ inline void log_pipe_info(nng_pipe p, const char *info)
     spdlog::info("{}: {}={}", info, NNG_OPT_REMADDR, remoteAddress);
 }
 
-using retry_predicate = std::function<bool ()>;
+// 'res' is the result of the last nng function call.
+using retry_predicate = std::function<bool (int res)>;
 
 class RetryNTimes
 {
@@ -213,7 +214,7 @@ class RetryNTimes
             : maxTries_(maxTries)
         {}
 
-        bool operator()()
+        bool operator()(int)
         {
             return attempt_++ < maxTries_;
         }
@@ -242,7 +243,7 @@ inline int send_message_retry(nng_socket socket, nng_msg *msg, retry_predicate r
             if (res == NNG_ETIMEDOUT)
                 spdlog::trace("send_message_retry: {} - send timeout (msg={})", debugInfo, fmt::ptr(msg));
 
-            if (!rp())
+            if (!rp(res))
                 return res;
         }
     } while (res == NNG_ETIMEDOUT);
@@ -286,7 +287,7 @@ std::optional<T> msg_trim_read(nng_msg *msg)
 {
     const auto oldlen = nng_msg_len(msg); (void) oldlen;
     if (nng_msg_len(msg) < sizeof(T))
-        return {};
+        return std::nullopt;
 
     T result = *reinterpret_cast<T *>(nng_msg_body(msg));
     nng_msg_trim(msg, sizeof(T));