diff --git a/lib/vtls/mbedtls.c b/lib/vtls/mbedtls.c
index f0048ef49..6fc7214ac 100644
--- a/lib/vtls/mbedtls.c
+++ b/lib/vtls/mbedtls.c
@@ -391,13 +391,12 @@ mbed_connect_step1(struct connectdata *conn,
     mbedtls_ssl_conf_own_cert(&connssl->config,
                               &connssl->clicert, &connssl->pk);
   }
-  if(!Curl_inet_pton(AF_INET, conn->host.name, &addr) &&
-#ifdef ENABLE_IPV6
-     !Curl_inet_pton(AF_INET6, conn->host.name, &addr) &&
-#endif
-     sni && mbedtls_ssl_set_hostname(&connssl->ssl, conn->host.name)) {
-    infof(data, "WARNING: failed to configure "
-          "server name indication (SNI) TLS extension\n");
+  if(mbedtls_ssl_set_hostname(&connssl->ssl, conn->host.name)) {
+    /* mbedtls_ssl_set_hostname() sets the name to use in CN/SAN checks *and*
+       the name to set in the SNI extension. So even if curl connects to a
+       host specified as an IP address, this function must be used. */
+    failf(data, "couldn't set hostname in mbedTLS");
+    return CURLE_SSL_CONNECT_ERROR;
   }
 
 #ifdef HAS_ALPN
diff --git a/lib/vtls/polarssl.c b/lib/vtls/polarssl.c
index aa4da3f6a..0e8b0f500 100644
--- a/lib/vtls/polarssl.c
+++ b/lib/vtls/polarssl.c
@@ -354,13 +354,12 @@ polarssl_connect_step1(struct connectdata *conn,
   ssl_set_own_cert_rsa(&connssl->ssl,
                        &connssl->clicert, &connssl->rsa);
 
-  if(!Curl_inet_pton(AF_INET, conn->host.name, &addr) &&
-#ifdef ENABLE_IPV6
-     !Curl_inet_pton(AF_INET6, conn->host.name, &addr) &&
-#endif
-     sni && ssl_set_hostname(&connssl->ssl, conn->host.name)) {
-     infof(data, "WARNING: failed to configure "
-                 "server name indication (SNI) TLS extension\n");
+  if(ssl_set_hostname(&connssl->ssl, conn->host.name)) {
+    /* ssl_set_hostname() sets the name to use in CN/SAN checks *and* the name
+       to set in the SNI extension. So even if curl connects to a host
+       specified as an IP address, this function must be used. */
+    failf(data, "couldn't set hostname in PolarSSL");
+    return CURLE_SSL_CONNECT_ERROR;
   }
 
 #ifdef HAS_ALPN