diff --git a/embed/trezorhal/usb.c b/embed/trezorhal/usb.c
index df5c3b51d..4e93e29a9 100644
--- a/embed/trezorhal/usb.c
+++ b/embed/trezorhal/usb.c
@@ -200,12 +200,12 @@ static uint8_t *usb_get_serial_str_descriptor(USBD_SpeedTypeDef speed, uint16_t
 }
 
 static uint8_t *usb_get_config_str_descriptor(USBD_SpeedTypeDef speed, uint16_t *length) {
-    *length = 0;
+    USBD_GetString(UNCONST(""), usb_str_buf, length);
     return usb_str_buf;
 }
 
 static uint8_t *usb_get_interface_str_descriptor(USBD_SpeedTypeDef speed, uint16_t *length) {
-    *length = 0;
+    USBD_GetString(UNCONST(""), usb_str_buf, length);
     return usb_str_buf;
 }