1 files changed, 4 insertions, 0 deletions
diff --git a/src/main.c b/src/main.c
index cfff1f982..1c707f89f 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1765,6 +1765,10 @@ static int sockoptcallback(void *clientp, curl_socket_t curlfd,
           return 0;
         }
 #endif
+#if !defined(TCP_KEEPIDLE) || !defined(TCP_KEEPINTVL)
+        warnf(clientp, "Keep-alive functionality somewhat crippled due to "
+              "missing support in your operating system!\n");
+#endif
       }
     }
     break;