diff --git a/drivers/usb/gadget/function/f_accessory.c b/drivers/usb/gadget/function/f_accessory.c
index 1ef3442cf618..7950f25136a5 100644
--- a/drivers/usb/gadget/function/f_accessory.c
+++ b/drivers/usb/gadget/function/f_accessory.c
@@ -346,6 +346,7 @@ static void acc_complete_set_string(struct usb_ep *ep, struct usb_request *req)
 	struct acc_dev	*dev = ep->driver_data;
 	char *string_dest = NULL;
 	int length = req->actual;
+	unsigned long flags;
 
 	if (req->status != 0) {
 		pr_err("acc_complete_set_string, err %d\n", req->status);
@@ -371,22 +372,26 @@ static void acc_complete_set_string(struct usb_ep *ep, struct usb_request *req)
 	case ACCESSORY_STRING_SERIAL:
 		string_dest = dev->serial;
 		break;
-	}
-	if (string_dest) {
-		unsigned long flags;
-
-		if (length >= ACC_STRING_SIZE)
-			length = ACC_STRING_SIZE - 1;
-
-		spin_lock_irqsave(&dev->lock, flags);
-		memcpy(string_dest, req->buf, length);
-		/* ensure zero termination */
-		string_dest[length] = 0;
-		spin_unlock_irqrestore(&dev->lock, flags);
-	} else {
+	default:
 		pr_err("unknown accessory string index %d\n",
-			dev->string_index);
+					dev->string_index);
+		return;
 	}
+
+	if (!length) {
+		pr_debug("zero length for accessory string index %d\n",
+						dev->string_index);
+		return;
+	}
+
+	if (length >= ACC_STRING_SIZE)
+		length = ACC_STRING_SIZE - 1;
+
+	spin_lock_irqsave(&dev->lock, flags);
+	memcpy(string_dest, req->buf, length);
+	/* ensure zero termination */
+	string_dest[length] = 0;
+	spin_unlock_irqrestore(&dev->lock, flags);
 }
 
 static void acc_complete_set_hid_report_desc(struct usb_ep *ep,