diff --git a/src/stm32/stm32l4.c b/src/stm32/stm32l4.c
index 8fb50a23..b5c939bb 100644
--- a/src/stm32/stm32l4.c
+++ b/src/stm32/stm32l4.c
@@ -7,7 +7,6 @@
 #include "autoconf.h" // CONFIG_CLOCK_REF_FREQ
 #include "board/armcm_boot.h" // VectorTable
 #include "board/irq.h" // irq_disable
-#include "board/usb_cdc.h" // usb_request_bootloader
 #include "command.h" // DECL_CONSTANT_STR
 #include "internal.h" // enable_pclock
 #include "sched.h" // sched_main
@@ -68,25 +67,6 @@ gpio_clock_enable(GPIO_TypeDef *regs)
     RCC->AHB2ENR;
 }
 
-#define USB_BOOT_FLAG_ADDR (CONFIG_RAM_START + CONFIG_RAM_SIZE - 4096)
-#define USB_BOOT_FLAG 0x55534220424f4f54 // "USB BOOT"
-
-// Handle USB reboot requests
-void
-usb_request_bootloader(void)
-{
-    irq_disable();
-    // System DFU Bootloader
-    *(uint64_t*)USB_BOOT_FLAG_ADDR = USB_BOOT_FLAG;
-    NVIC_SystemReset();
-}
-
-void
-bootloader_request(void)
-{
-    usb_request_bootloader();
-}
-
 #if !CONFIG_STM32_CLOCK_REF_INTERNAL
 DECL_CONSTANT_STR("RESERVE_PINS_crystal", "PC14,PC15");
 #endif
@@ -154,16 +134,53 @@ clock_setup(void)
         ;
 }
 
+
+/****************************************************************
+ * Bootloader
+ ****************************************************************/
+
+#define USB_BOOT_FLAG_ADDR (CONFIG_RAM_START + CONFIG_RAM_SIZE - 4096)
+#define USB_BOOT_FLAG 0x55534220424f4f54 // "USB BOOT"
+
+// Flag that bootloader is desired and reboot
+static void
+usb_reboot_for_dfu_bootloader(void)
+{
+    irq_disable();
+    // System DFU Bootloader
+    *(uint64_t*)USB_BOOT_FLAG_ADDR = USB_BOOT_FLAG;
+    NVIC_SystemReset();
+}
+
+// Check if rebooting into system DFU Bootloader
+static void
+check_usb_dfu_bootloader(void)
+{
+    if (!CONFIG_USB || *(uint64_t*)USB_BOOT_FLAG_ADDR != USB_BOOT_FLAG)
+        return;
+    *(uint64_t*)USB_BOOT_FLAG_ADDR = 0;
+    uint32_t *sysbase = (uint32_t*)0x1fff0000;
+    asm volatile("mov sp, %0\n bx %1"
+                 : : "r"(sysbase[0]), "r"(sysbase[1]));
+}
+
+// Handle USB reboot requests
+void
+bootloader_request(void)
+{
+    usb_reboot_for_dfu_bootloader();
+}
+
+
+/****************************************************************
+ * Startup
+ ****************************************************************/
+
 // Main entry point - called from armcm_boot.c:ResetHandler()
 void
 armcm_main(void)
 {
-    if (CONFIG_USBSERIAL && *(uint64_t*)USB_BOOT_FLAG_ADDR == USB_BOOT_FLAG) {
-        *(uint64_t*)USB_BOOT_FLAG_ADDR = 0;
-        uint32_t *sysbase = (uint32_t*)0x1fff0000;
-        asm volatile("mov sp, %0\n bx %1"
-                     : : "r"(sysbase[0]), "r"(sysbase[1]));
-    }
+    check_usb_dfu_bootloader();
 
     // Run SystemInit() and then restore VTOR
     SystemInit();