diff --git a/libfreefare/freefare.c b/libfreefare/freefare.c
index bd1b380..2e17db8 100644
--- a/libfreefare/freefare.c
+++ b/libfreefare/freefare.c
@@ -28,11 +28,14 @@
 
 #define NXP_MANUFACTURER_CODE 0x04
 
+/* Number of bytes of ATS to compare */
+#define ATS_LENGTH 4
+
 struct supported_tag supported_tags[] = {
     { CLASSIC_1K, "Mifare Classic 1k",            0x08, 0, { 0x00 } },
     { CLASSIC_4K, "Mifare Classic 4k",            0x18, 0, { 0x00 } },
     { CLASSIC_4K, "Mifare Classic 4k (Emulated)", 0x38, 0, { 0x00 } },
-    { DESFIRE,    "Mifare DESFire",               0x20, 5, { 0x75, 0x77, 0x81, 0x02, 0x80 }},
+    { DESFIRE,    "Mifare DESFire",               0x20, 5, { 0x75, 0x77, 0x81, 0x02 /*, 0xXX */ }},
     { ULTRALIGHT, "Mifare UltraLight",            0x00, 0, { 0x00 } },
 };
 
@@ -51,7 +54,7 @@ freefare_tag_new (nfc_device_t *device, nfc_iso14443a_info_t nai)
 	if (((nai.szUidLen == 4) || (nai.abtUid[0] == NXP_MANUFACTURER_CODE)) &&
 	    (nai.btSak == supported_tags[i].SAK) &&
 	    (nai.szAtsLen == supported_tags[i].ATS_length) &&
-	    (0 == memcmp (nai.abtAts, supported_tags[i].ATS, supported_tags[i].ATS_length))) {
+	    (0 == memcmp (nai.abtAts, supported_tags[i].ATS, ATS_LENGTH))) {
 
 	    tag_info = &(supported_tags[i]);
 	    found = true;