diff --git a/Tests/IBANTest.php b/Tests/IBANTest.php
new file mode 100644
index 0000000..d0b6e0b
--- /dev/null
+++ b/Tests/IBANTest.php
@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the library "QRPlatba".
+ *
+ * (c) Dennis Fridrich <fridrich.dennis@gmail.com>
+ *
+ * For the full copyright and license information,
+ * please view LICENSE.
+ */
+
+use Defr\QRPlatba\QRPlatba;
+
+/**
+ * Class QRPlatbaTest.
+ */
+class IBANTest extends PHPUnit_Framework_TestCase
+{
+
+    public function testAccountHigherThanMaxInt()
+    {
+        $string = QRPlatba::accountToIban('2501301193/2010');
+
+        $this->assertSame(
+            'CZ3620100000002501301193',
+            $string
+        );
+    }
+
+}
diff --git a/src/QRPlatba.php b/src/QRPlatba.php
index d838702..9507f62 100644
--- a/src/QRPlatba.php
+++ b/src/QRPlatba.php
@@ -346,7 +346,7 @@ public static function accountToIban($accountNumber)
             list($pre, $acc) = explode('-', $accountNumber[0]);
         }
 
-        $accountPart = sprintf('%06d%010d', $pre, $acc);
+        $accountPart = sprintf('%06d%010s', $pre, $acc);
         $iban = 'CZ00'.$bank.$accountPart;
 
         $alfa = 'A B C D E F G H I J K L M N O P Q R S T U V W X Y Z';
@@ -360,7 +360,7 @@ public static function accountToIban($accountNumber)
             mb_substr($iban, 4, mb_strlen($iban) - 4).mb_substr($iban, 0, 2).'00'
         );
         $controlegetal = 98 - (int) bcmod($controlegetal, 97);
-        $iban = sprintf('CZ%02d%04d%06d%010d', $controlegetal, $bank, $pre, $acc);
+        $iban = sprintf('CZ%02d%04d%06d%010s', $controlegetal, $bank, $pre, $acc);
 
         return $iban;
     }