diff --git a/hid/__init__.py b/hid/__init__.py
index 752ddf5..69d82eb 100644
--- a/hid/__init__.py
+++ b/hid/__init__.py
@@ -174,7 +174,8 @@ def __init__(self, vid=None, pid=None, serial=None, path=None):
             raise ValueError('specify vid/pid or path')
 
         if not self.__dev:
-            raise HIDException('unable to open device')
+            err = hidapi.hid_error(0)
+            raise HIDException('unable to open device: ' + err)
 
     def __enter__(self):
         return self