diff --git a/ports/stm/mpconfigport.mk b/ports/stm/mpconfigport.mk
index 19f9ffa44c..b827aa48b9 100644
--- a/ports/stm/mpconfigport.mk
+++ b/ports/stm/mpconfigport.mk
@@ -7,6 +7,7 @@ ifeq ($(MCU_VARIANT),STM32F405xx)
 	CIRCUITPY_FRAMEBUFFERIO ?= 1
 	CIRCUITPY_RGBMATRIX ?= 1
 	CIRCUITPY_SDIOIO ?= 1
+	USB_NUM_EP = 4
 endif
 
 ifeq ($(MCU_SERIES),F4)
diff --git a/tools/gen_usb_descriptor.py b/tools/gen_usb_descriptor.py
index baee8cad7b..adf0d8270d 100644
--- a/tools/gen_usb_descriptor.py
+++ b/tools/gen_usb_descriptor.py
@@ -382,8 +382,9 @@ if args.max_ep != 0:
     for interface in interfaces:
         for subdescriptor in interface.subdescriptors:
             endpoint_address = getattr(subdescriptor, 'bEndpointAddress', 0) & 0x7f
-            if endpoint_address > args.max_ep:
-                raise ValueError("Endpoint address %d of %s may not exceed %d" % (endpoint_address & 0x7f, interface.description, args.max_ep))
+            print("Endpoint %d - vs max_ep %d" % (endpoint_address, args.max_ep))
+            if endpoint_address >= args.max_ep:
+                raise ValueError("Endpoint address %d of %s must be less than %d" % (endpoint_address & 0x7f, interface.description, args.max_ep))
 else:
     print("Unable to check whether maximum number of endpoints is respected", file=sys.stderr)