diff --git a/Labs/05. Main decoder/lab_05.tb_decoder.sv b/Labs/05. Main decoder/lab_05.tb_decoder.sv
index 2019d0b..dd2d245 100644
--- a/Labs/05. Main decoder/lab_05.tb_decoder.sv	
+++ b/Labs/05. Main decoder/lab_05.tb_decoder.sv	
@@ -676,8 +676,9 @@ module lab_05_tb_decoder();
               ALU_SRA  : instr_str = "(      SRA     )";
               ALU_SRL  : instr_str = "(      SRL     )";
               ALU_SLL  : instr_str = "(      SLL     )";
+              ALU_SLTS : instr_str = "(      SLT     )";
               ALU_SLTU : instr_str = "(      SLTU    )";
-              default   : instr_str = "(  illegal_OP  )";
+              default  : instr_str = "(  illegal_OP  )";
             endcase
           else instr_str = "(  illegal_OP  )";
         end