diff --git a/libfreefare/mifare_desfire_key.c b/libfreefare/mifare_desfire_key.c
index 3968cd9..7a0a9be 100644
--- a/libfreefare/mifare_desfire_key.c
+++ b/libfreefare/mifare_desfire_key.c
@@ -136,12 +136,33 @@ mifare_desfire_key_set_version(MifareDESFireKey key, uint8_t version)
 	uint8_t version_bit = ((version & (1 << (7 - n))) >> (7 - n));
 	key->data[n] &= 0xfe;
 	key->data[n] |= version_bit;
-	if (key->type == T_DES) {
+	switch (key->type) {
+	case T_DES:
+		// DESFire cards always treat DES keys as special cases of 2K3DES
+		// keys. The DESFire functional specification explicitly points
+		// out that if the subkeys of a 2K3DES key are exactly identical
+		// (including parity bits), then (and only then) is the key treated
+		// as a DES key for authentication purposes. Specifically, the
+		// version/parity bits must be idential, as well as the rest of the
+		// key, otherwise the PICC will treat it as a 2K3DES key.  This
+		// next line ensure that.
 	    key->data[n + 8] = key->data[n];
-	} else {
-	    // Write ~version to avoid turning a 3DES key into a DES key
+	    break;
+	case T_3DES:
+		// But what if we really did want the PICC to treat the key as a
+		// real 2K3DES key, even if the actual 56 bits of the subkeys did
+		// match? To ensure that such as case still works (largely because
+		// the datasheet implies authentication would behave differently
+		// otherwise), we need to ensure that the parity bits on the subkeys
+		// explicitly do not match. The easiest way to ensure that is to
+		// always write the bits of `~version` to the parity bits of the
+		// second subkey. Note that this would only have an effect at the
+		// PICC level if the subkeys were otherwise identical.
 	    key->data[n + 8] &= 0xfe;
-	    key->data[n + 8] |= ~version_bit;
+	    key->data[n + 8] |= !version_bit;
+	    break;
+	default:
+	    break;
 	}
     }
 }
diff --git a/test/test_mifare_desfire_key.c b/test/test_mifare_desfire_key.c
index 5c428e4..3c00cf7 100644
--- a/test/test_mifare_desfire_key.c
+++ b/test/test_mifare_desfire_key.c
@@ -1,6 +1,7 @@
 #include <cutter.h>
 
 #include <freefare.h>
+#include "freefare_internal.h"
 
 
 void
@@ -14,6 +15,8 @@ test_mifare_desfire_key(void)
     key = mifare_desfire_des_key_new(key1_des_data);
     version = mifare_desfire_key_get_version(key);
     cut_assert_equal_int(0x00, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0x55);
+    cut_assert_equal_memory(key1_des_data, sizeof(key1_des_data), key->data, sizeof(key1_des_data), cut_message("Version change corrupted key"));
     mifare_desfire_key_free(key);
 
     key = mifare_desfire_des_key_new_with_version(key1_des_data);
@@ -22,6 +25,8 @@ test_mifare_desfire_key(void)
     mifare_desfire_key_set_version(key, 0xaa);
     version = mifare_desfire_key_get_version(key);
     cut_assert_equal_int(0xaa, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0x55);
+    cut_assert_equal_memory(key1_des_data, sizeof(key1_des_data), key->data, sizeof(key1_des_data), cut_message("Version change corrupted key"));
     mifare_desfire_key_free(key);
 
 
@@ -38,11 +43,13 @@ test_mifare_desfire_key(void)
     mifare_desfire_key_free(key);
 
 
-    uint8_t key1_3des_data[16] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0XEE, 0xFF };
+    uint8_t key1_3des_data[16] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x89, 0x98, 0xAB, 0xBA, 0xCD, 0xDC, 0xEF, 0xFE };
 
     key = mifare_desfire_3des_key_new(key1_3des_data);
     version = mifare_desfire_key_get_version(key);
     cut_assert_equal_int(0x00, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0x55);
+    cut_assert_equal_memory(key1_3des_data, sizeof(key1_3des_data), key->data, sizeof(key1_3des_data), cut_message("Version change corrupted key"));
     mifare_desfire_key_free(key);
 
     key = mifare_desfire_3des_key_new_with_version(key1_3des_data);
@@ -51,9 +58,11 @@ test_mifare_desfire_key(void)
     mifare_desfire_key_set_version(key, 0xaa);
     version = mifare_desfire_key_get_version(key);
     cut_assert_equal_int(0xaa, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0x55);
+    cut_assert_equal_memory(key1_3des_data, sizeof(key1_3des_data), key->data, sizeof(key1_3des_data), cut_message("Version change corrupted key"));
     mifare_desfire_key_free(key);
 
-    uint8_t key2_3des_data[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0X01, 0x00, 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77 };
+    uint8_t key2_3des_data[16] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77 };
 
     key = mifare_desfire_3des_key_new(key2_3des_data);
     version = mifare_desfire_key_get_version(key);
@@ -65,7 +74,7 @@ test_mifare_desfire_key(void)
     cut_assert_equal_int(0x02, version, cut_message("Wrong MifareDESFireKey version"));
     mifare_desfire_key_free(key);
 
-    uint8_t key3_3des_data[16] = { 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0X00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x77 };
+    uint8_t key3_3des_data[16] = { 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x77 };
 
     key = mifare_desfire_3des_key_new(key3_3des_data);
     version = mifare_desfire_key_get_version(key);
@@ -76,4 +85,43 @@ test_mifare_desfire_key(void)
     version = mifare_desfire_key_get_version(key);
     cut_assert_equal_int(0x10, version, cut_message("Wrong MifareDESFireKey version"));
     mifare_desfire_key_free(key);
+
+    uint8_t key1_3k3des_data[24] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08 };
+
+    key = mifare_desfire_3k3des_key_new(key1_3k3des_data);
+    version = mifare_desfire_key_get_version(key);
+    cut_assert_equal_int(0x00, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0x55);
+    cut_assert_equal_memory(key1_3k3des_data, sizeof(key1_3k3des_data), key->data, sizeof(key1_3k3des_data), cut_message("Version change corrupted key"));
+    mifare_desfire_key_free(key);
+
+    key = mifare_desfire_3k3des_key_new_with_version(key1_3k3des_data);
+    version = mifare_desfire_key_get_version(key);
+    cut_assert_equal_int(0x55, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0xaa);
+    version = mifare_desfire_key_get_version(key);
+    cut_assert_equal_int(0xaa, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0x55);
+    cut_assert_equal_memory(key1_3k3des_data, sizeof(key1_3k3des_data), key->data, sizeof(key1_3k3des_data), cut_message("Version change corrupted key"));
+    mifare_desfire_key_free(key);
+
+
+    uint8_t key1_aes_data[16] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF };
+
+    key = mifare_desfire_aes_key_new(key1_aes_data);
+    version = mifare_desfire_key_get_version(key);
+    cut_assert_equal_int(0x00, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0x55);
+    cut_assert_equal_memory(key1_aes_data, sizeof(key1_aes_data), key->data, sizeof(key1_aes_data), cut_message("Version change corrupted key"));
+    mifare_desfire_key_free(key);
+
+    key = mifare_desfire_aes_key_new_with_version(key1_aes_data, 0x33);
+    version = mifare_desfire_key_get_version(key);
+    cut_assert_equal_int(0x33, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0xaa);
+    version = mifare_desfire_key_get_version(key);
+    cut_assert_equal_int(0xaa, version, cut_message("Wrong MifareDESFireKey version"));
+    mifare_desfire_key_set_version(key, 0x33);
+    cut_assert_equal_memory(key1_aes_data, sizeof(key1_aes_data), key->data, sizeof(key1_aes_data), cut_message("Version change corrupted key"));
+    mifare_desfire_key_free(key);
 }