diff --git a/src/libprs500/devices/libusb.py b/src/libprs500/devices/libusb.py
index 0d0f3defaf..c7182b3cc2 100644
--- a/src/libprs500/devices/libusb.py
+++ b/src/libprs500/devices/libusb.py
@@ -145,6 +145,8 @@ class Bus(Structure):
         TODO: Check if exploring children is neccessary (e.g. with an external hub)
         """
         def fget(self):
+            if _libusb is None:
+                return []
             if _libusb.usb_find_devices() < 0:
                 raise Error('Unable to search for USB devices')
             ndev = self.devices