diff --git a/python/usb.py b/python/usb.py
index a43bb51d..0ea0020b 100644
--- a/python/usb.py
+++ b/python/usb.py
@@ -34,9 +34,15 @@ class STBootloaderUSBHandle(BaseSTBootloaderHandle):
   def __init__(self, libusb_device, libusb_handle):
     self._libusb_handle = libusb_handle
 
-    # TODO: Find a way to detect F4 vs F2
-    # TODO: also check F4 BCD, don't assume in else
-    self._mcu_type = McuType.H7 if libusb_device.getbcdDevice() == 512 else McuType.F4
+    # lsusb -v | grep Flash
+    # iInterface  4 @Internal Flash  /0x08000000/04*016Kg,01*064Kg,011*128Kg
+    out = libusb_handle.controlRead(0x80, 0x06, 0x0300 | 4, 0, 255)
+    flash_desc = bytes(out[2:]).decode('utf-16le')
+    sector_count = sum([int(s.split('*')[0]) for s in flash_desc.split('/')[-1].split(',')])
+
+    mcu_by_sector_count = {len(m.config.sector_sizes): m for m in McuType}
+    assert sector_count in mcu_by_sector_count, f"Unkown MCU: {sector_count=}"
+    self._mcu_type = mcu_by_sector_count[sector_count]
 
   def _status(self) -> None:
     while 1: