diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/NfcActivity.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/NfcActivity.java
index fb2209d3e..7aa09e801 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/NfcActivity.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/ui/NfcActivity.java
@@ -208,7 +208,7 @@ public class NfcActivity extends ActionBarActivity {
             + "20" // INS
             + "00" // P1
             + "82" // P2 (PW1)
-            + String.format("%02d", mPin.length()) // Lc
+            + String.format("%02x", mPin.length()) // Lc
             + Hex.toHexString(mPin.getBytes());
         if ( ! card(login).equals(accepted)) { // login
             toast("Wrong PIN!");