Index: src/natools-smaz_generic.adb
==================================================================
--- src/natools-smaz_generic.adb
+++ src/natools-smaz_generic.adb
@@ -198,10 +198,11 @@
 
          if Verbatim_Length > 0 then
             Skip_Verbatim (Input, Input_Index, Verbatim_Length);
             Result := Result + Verbatim_Length;
          else
+            exit when not Is_Valid_Code (Dict, Code);
             Result := Result + Dict_Entry_Length (Dict, Code);
          end if;
       end loop;
 
       return Result;
@@ -231,10 +232,12 @@
               (Input, Input_Index,
                Output_Buffer
                  (Output_Last + 1 .. Output_Last + Verbatim_Length));
             Output_Last := Output_Last + Verbatim_Length;
          else
+            exit when not Is_Valid_Code (Dict, Code);
+
             declare
                Decoded : constant String := Dict_Entry (Dict, Code);
             begin
                Output_Buffer (Output_Last + 1 .. Output_Last + Decoded'Length)
                  := Decoded;