diff --git a/libfreefare/mifare_desfire_authenticate.c b/libfreefare/mifare_desfire_authenticate.c
index b851818..91d3dca 100644
--- a/libfreefare/mifare_desfire_authenticate.c
+++ b/libfreefare/mifare_desfire_authenticate.c
@@ -236,7 +236,7 @@ key_macing_length (const MifareDESFireKey key)
 size_t
 padded_data_length (const size_t nbytes, const size_t block_size)
 {
-    if (nbytes % block_size)
+    if ((!nbytes) || (nbytes % block_size))
 	return ((nbytes / block_size) + 1) * block_size;
     else
 	return nbytes;
diff --git a/test/test_mifare_desfire_des.c b/test/test_mifare_desfire_des.c
index 54b63f8..a4b9404 100644
--- a/test/test_mifare_desfire_des.c
+++ b/test/test_mifare_desfire_des.c
@@ -71,3 +71,22 @@ test_mifare_desfire_des_send (void)
 
     mifare_desfire_key_free (key);
 }
+
+void
+test_mifare_desfire_padded_data_length (void)
+{
+    size_t res;
+
+    res = padded_data_length (0, 8);
+    cut_assert_equal_int (res, 8, cut_message ("Invalid size"));
+    res = padded_data_length (1, 8);
+    cut_assert_equal_int (res, 8, cut_message ("Invalid size"));
+    res = padded_data_length (8, 8);
+    cut_assert_equal_int (res, 8, cut_message ("Invalid size"));
+    res = padded_data_length (9, 8);
+    cut_assert_equal_int (res, 16, cut_message ("Invalid size"));
+    res = padded_data_length (0, 16);
+    cut_assert_equal_int (res, 16, cut_message ("Invalid size"));
+    res = padded_data_length (33, 16);
+    cut_assert_equal_int (res, 48, cut_message ("Invalid size"));
+}