diff --git a/src/tls.c b/src/tls.c
index 9fe0109e..d22387ad 100644
--- a/src/tls.c
+++ b/src/tls.c
@@ -272,7 +272,7 @@ fail:
 int mg_tls_handshake(struct mg_connection *c) {
   struct mg_tls *tls = (struct mg_tls *) c->tls;
   int rc;
-  SSL_set_fd(tls->ssl, (int) c->fd);
+  SSL_set_fd(tls->ssl, (ssize_t) c->fd);
   rc = c->is_client ? SSL_connect(tls->ssl) : SSL_accept(tls->ssl);
   if (rc == 1) {
     LOG(LL_DEBUG, ("%lu success", c->id));