diff --git a/src/calibre/devices/__init__.py b/src/calibre/devices/__init__.py
index feaeffdcd9..f2065dd632 100644
--- a/src/calibre/devices/__init__.py
+++ b/src/calibre/devices/__init__.py
@@ -60,8 +60,10 @@ def debug(ioreg_to_tmp=False, buf=None):
         if isosx:
             from calibre.devices.usbms.device import Device
             mount = repr(Device.osx_run_mount())
-            ioreg = Device.run_ioreg()
-            ioreg = 'Output from mount:\n\n'+mount+'\n\n'+ioreg
+            drives = pprint.pformat(Device.osx_get_usb_drives())
+            ioreg = 'Output from mount:\n'+mount+'\n\n'
+            ioreg += 'Output from osx_get_usb_drives:\n'+drives+'\n\n'
+            ioreg += Device.run_ioreg()
         connected_devices = []
         for dev in device_plugins():
             out('Looking for', dev.__class__.__name__)
diff --git a/src/calibre/devices/usbms/device.py b/src/calibre/devices/usbms/device.py
index 0f3c550291..1db85ea18b 100644
--- a/src/calibre/devices/usbms/device.py
+++ b/src/calibre/devices/usbms/device.py
@@ -333,10 +333,14 @@ class Device(DeviceConfig, DevicePlugin):
                     raise
             time.sleep(2)
 
-    def _osx_bsd_names(self):
+    @classmethod
+    def osx_get_usb_drives(cls):
         if usbobserver_err:
             raise RuntimeError('Failed to load usbobserver: '+usbobserver_err)
-        drives = usbobserver.get_usb_drives()
+        return usbobserver.get_usb_drives()
+
+    def _osx_bsd_names(self):
+        drives = self.osx_get_usb_drives()
         matches = []
         d = self.detected_device
         if d.serial: