Index: src/natools-smaz_implementations-base_64.adb
==================================================================
--- src/natools-smaz_implementations-base_64.adb
+++ src/natools-smaz_implementations-base_64.adb
@@ -58,12 +58,11 @@
          Offset := Offset_Backup;
          Code := 0;
 
       else
          Offset_Backup := Offset;
-         Verbatim_Length := (Natural (Code) - 61)
-                          * (Natural (Tools.Single_Byte_Padding'Last) + 1);
+         Verbatim_Length := (61 - Natural (Code)) * 4;
          Tools.Decode_Double (Input, Offset, Ignored, Code);
          Verbatim_Length := (Verbatim_Length + Natural (Code)) * 3 + 2;
          Offset := Offset_Backup;
          Code := 0;
       end if;