diff --git a/usbutils.c b/usbutils.c
index 13167af0..c793b9ab 100644
--- a/usbutils.c
+++ b/usbutils.c
@@ -2538,6 +2538,7 @@ void usb_buffer_disable(struct cgpu_info *cgpu)
 		cgusb->bufamt = 0;
 		cgusb->bufsiz = 0;
 		free(cgusb->buffer);
+		cgusb->buffer = NULL;
 	}
 }