diff --git a/lib/smb.c b/lib/smb.c
index 326b231c61dcff03758dae9467e98cc63502ea11..d990a892f62e744e7256ae50d5c70d46ba8007cd 100644
--- a/lib/smb.c
+++ b/lib/smb.c
@@ -216,6 +216,10 @@ static CURLcode smb_connect(struct connectdata *conn, bool *done)
 
   (void) done;
 
+  /* Check we have a username and password to authenticate with */
+  if(!conn->bits.user_passwd)
+    return CURLE_LOGIN_DENIED;
+
   /* Initialize the connection state */
   memset(smbc, 0, sizeof(*smbc));
   smbc->state = SMB_CONNECTING;