diff --git a/bankbarcode/cuaderno57.py b/bankbarcode/cuaderno57.py
index dea428b..e6b6594 100644
--- a/bankbarcode/cuaderno57.py
+++ b/bankbarcode/cuaderno57.py
@@ -273,6 +273,8 @@ def checksum(self):
             + int(self.notice) \
             + self.amount100()
         decimals = int(Decimal(sum) / 97 % 1 * 100)
+        if not decimals:
+            return '00'
         return unicode(100 - decimals).zfill(2)
 
     def code(self):
diff --git a/spec/cuaderno57_Recibo507_checksum_spec.py b/spec/cuaderno57_Recibo507_checksum_spec.py
index 38c5e3a..7ecc89d 100644
--- a/spec/cuaderno57_Recibo507_checksum_spec.py
+++ b/spec/cuaderno57_Recibo507_checksum_spec.py
@@ -28,3 +28,12 @@
         amount = '37.62'
         checksum = '56'
         expect(Recibo507(entity, suffix, ref, notice, amount).checksum()).to(equal(checksum))
+
+    with it('accomplish another example'):
+        entity = '22350466'
+        suffix = '501'
+        ref = '00000085501'
+        notice = '130516'
+        amount = '56.92'
+        checksum = '00'
+        expect(Recibo507(entity, suffix, ref, notice, amount).checksum()).to(equal(checksum))