diff --git a/lib/ftp.c b/lib/ftp.c
index 471bd6edfd4eada910cf0a22d143987acef093af..5b79662c2f25e640216a457c912174d491716e60 100644
--- a/lib/ftp.c
+++ b/lib/ftp.c
@@ -158,6 +158,7 @@ static CURLcode AllowServerConnect(struct SessionHandle *data,
       infof(data, "Connection accepted from server\n");
 
       conn->secondarysocket = s;
+      Curl_nonblock(s, TRUE); /* enable non-blocking */
     }
     break;
   }