diff --git a/lib/usb.rb b/lib/usb.rb
index 1d8ae5f..3a0d572 100644
--- a/lib/usb.rb
+++ b/lib/usb.rb
@@ -219,7 +219,7 @@ def USB.dev_string(base_class, sub_class, protocol)
     elsif desc = CLASS_CODES_HASH1[base_class]
       desc + " (%02x,%02x)" % [sub_class, protocol]
     else
-      "Unkonwn(%02x,%02x,%02x)" % [base_class, sub_class, protocol]
+      "Unknown(%02x,%02x,%02x)" % [base_class, sub_class, protocol]
     end
   end
   # :startdoc: