--- a/src/mbedtls/engine.c
+++ b/src/mbedtls/engine.c
@@ -111,7 +111,7 @@
 tlsuv_engine_t new_mbedtls_engine(tls_context *ctx, const char *host);
 
 static void mbedtls_set_io(tlsuv_engine_t, io_ctx , io_read , io_write );
-static void mbedtls_set_fd(tlsuv_engine_t, uv_os_fd_t );
+static void mbedtls_set_fd(tlsuv_engine_t, tlsuv_sock_t );
 
 static tls_handshake_state mbedtls_hs_state(tlsuv_engine_t engine);
 static tls_handshake_state
@@ -701,10 +701,10 @@
     mbedtls_ssl_set_bio(eng->ssl, eng, engine_io_write, engine_io_read, NULL);
 }
 
-static void mbedtls_set_fd(tlsuv_engine_t e, uv_os_fd_t fd) {
+static void mbedtls_set_fd(tlsuv_engine_t e, tlsuv_sock_t fd) {
     struct mbedtls_engine *eng = (struct mbedtls_engine *) e;
     assert(eng->io == NULL);
-    eng->io_fd = fd;
+    eng->io_fd = (uv_os_fd_t)fd;
     eng->io = &eng->io_fd;
     mbedtls_ssl_set_bio(eng->ssl, eng->io, mbedtls_net_send, mbedtls_net_recv, NULL);
 }