diff --git a/lib/pin_block.js b/lib/pin_block.js
index 24b7965..f442758 100644
--- a/lib/pin_block.js
+++ b/lib/pin_block.js
@@ -26,7 +26,7 @@ function pinBlock(pin) {
 function panBlock(pan) {
   const MAX_PAN_LENGTH = 12;
   const PAN_LENGTH = pan.toString().length;
-  const panBlockHex = `0000${pan.substring(PAN_LENGTH - MAX_PAN_LENGTH - 1, PAN_LENGTH - 1)}`;
+  const panBlockHex = `0000${pan.substring(PAN_LENGTH - MAX_PAN_LENGTH, PAN_LENGTH)}`;
 
   return panBlockHex;
 }