diff --git a/testhal/STM32F4xx/USB_CDC/main.c b/testhal/STM32F4xx/USB_CDC/main.c
index 02f7b4829..7c033e7eb 100644
--- a/testhal/STM32F4xx/USB_CDC/main.c
+++ b/testhal/STM32F4xx/USB_CDC/main.c
@@ -242,7 +242,7 @@ static const USBEndpointConfig ep1config = {
   0x0000,
   &ep1instate,
   NULL,
-  2,
+  4,
   NULL
 };
 
@@ -394,10 +394,34 @@ static void cmd_test(BaseSequentialStream *chp, int argc, char *argv[]) {
   chThdWait(tp);
 }
 
+static void cmd_usbblast(BaseSequentialStream *chp, int argc, char *argv[]) {
+  static uint8_t buf[512] =
+      "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+      "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+      "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+      "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+      "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+      "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+      "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
+      "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef";
+
+  (void)argv;
+  if (argc > 0) {
+    chprintf(chp, "Usage: test\r\n");
+    return;
+  }
+
+  while (chnGetTimeout((BaseChannel *)chp, TIME_IMMEDIATE) == Q_TIMEOUT) {
+    chSequentialStreamWrite(&SDU1, buf, sizeof buf);
+  }
+  chprintf(chp, "\r\n\nstopped\r\n");
+}
+
 static const ShellCommand commands[] = {
   {"mem", cmd_mem},
   {"threads", cmd_threads},
   {"test", cmd_test},
+  {"usbblast", cmd_usbblast},
   {NULL, NULL}
 };