diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c
index 83a4f0e6fb928799596b424b5b26c0ae3cead6f9..76ceca1f5c0d9cbffaf917892516b358af23e490 100644
--- a/hw/usb/dev-serial.c
+++ b/hw/usb/dev-serial.c
@@ -516,27 +516,16 @@ static USBDevice *usb_serial_init(USBBus *bus, const char *filename)
     char label[32];
     static int index;
 
-    while (*filename && *filename != ':') {
-        const char *p;
-
-        if (strstart(filename, "vendorid=", &p)) {
-            error_report("vendorid is not supported anymore");
-            return NULL;
-        } else if (strstart(filename, "productid=", &p)) {
-            error_report("productid is not supported anymore");
-            return NULL;
-        } else {
-            error_report("unrecognized serial USB option %s", filename);
-            return NULL;
-        }
-        while(*filename == ',')
-            filename++;
+    if (*filename == ':') {
+        filename++;
+    } else if (*filename) {
+        error_report("unrecognized serial USB option %s", filename);
+        return NULL;
     }
     if (!*filename) {
         error_report("character device specification needed");
         return NULL;
     }
-    filename++;
 
     snprintf(label, sizeof(label), "usbserial%d", index++);
     cdrv = qemu_chr_new(label, filename);