diff --git a/libusb/os/darwin_usb.c b/libusb/os/darwin_usb.c
index ff26800..93bf05c 100644
--- a/libusb/os/darwin_usb.c
+++ b/libusb/os/darwin_usb.c
@@ -1120,6 +1120,8 @@
       priv->dev = cached_device;
       darwin_ref_cached_device (priv->dev);
       dev->port_number    = cached_device->port;
+      /* the location ID encodes the path to the device. the top byte of the location ID contains the bus number
+         (numbered from 0). the remaining bytes can be used to construct the device tree for that bus. */
       dev->bus_number     = cached_device->location >> 24;
       assert(cached_device->address <= UINT8_MAX);
       dev->device_address = (uint8_t)cached_device->address;
diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index 9582fee..2773f71 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11638
+#define LIBUSB_NANO 11639