diff --git a/lib/pcsclite.js b/lib/pcsclite.js
index ed10230..f1da892 100644
--- a/lib/pcsclite.js
+++ b/lib/pcsclite.js
@@ -116,7 +116,7 @@ CardReader.prototype.SCARD_STATE_EMPTY = 0x0010;
 CardReader.prototype.SCARD_STATE_PRESENT = 0x0020;
 CardReader.prototype.SCARD_STATE_ATRMATCH = 0x0040;
 CardReader.prototype.SCARD_STATE_EXCLUSIVE = 0x0080;
-CardReader.prototype.CARD_STATE_INUSE = 0x0100;
+CardReader.prototype.SCARD_STATE_INUSE = 0x0100;
 CardReader.prototype.SCARD_STATE_MUTE = 0x0200;
 
 // extend prototype