diff --git a/vnc.c b/vnc.c
index ab1f044..c49ce61 100644
--- a/vnc.c
+++ b/vnc.c
@@ -2082,6 +2082,9 @@ int vnc_display_password(DisplayState *ds, const char *password)
 {
     VncDisplay *vs = ds ? (VncDisplay *)ds->opaque : vnc_display;
 
+    if (!vs)
+        return -1;
+
     if (vs->password) {
         qemu_free(vs->password);
         vs->password = NULL;
@@ -2090,6 +2093,9 @@ int vnc_display_password(DisplayState *ds, const char *password)
         if (!(vs->password = qemu_strdup(password)))
             return -1;
     }
+    if (vs->auth == VNC_AUTH_NONE) {
+        vs->auth = VNC_AUTH_VNC;
+    }
 
     return 0;
 }