diff --git a/src/arch/interface/quad.py b/src/arch/interface/quad.py
index fd5ac192b..a9e4140d4 100644
--- a/src/arch/interface/quad.py
+++ b/src/arch/interface/quad.py
@@ -10,7 +10,7 @@
 class Quad:
     """Implements a Quad code instruction."""
 
-    instr: str
+    instr: ICInstruction
     args: tuple[str, ...]
 
     def __init__(self, instr: ICInstruction, *args) -> None:
diff --git a/src/arch/z80/backend/icinstruction.py b/src/arch/z80/backend/icinstruction.py
index 6ecec1e2b..2ae2c19be 100644
--- a/src/arch/z80/backend/icinstruction.py
+++ b/src/arch/z80/backend/icinstruction.py
@@ -1,3 +1,4 @@
+from enum import StrEnum
 from functools import lru_cache
 from typing import Any
 
@@ -7,7 +8,7 @@
 
 
 # HINT: Do not use Enums here. They cannot be subclassed
-class ICInstruction:
+class ICInstruction(StrEnum):
     ADDU8 = "addu8"
     ADDI8 = "addi8"
     ADDI16 = "addi16"
diff --git a/src/arch/z80/backend/main.py b/src/arch/z80/backend/main.py
index 536868bdd..79d8d487f 100644
--- a/src/arch/z80/backend/main.py
+++ b/src/arch/z80/backend/main.py
@@ -145,7 +145,7 @@ class Backend(BackendInterface):
 
     def _set_quad_table(self):
         """Lowlevel (to ASM) instructions implementation"""
-        self._QUAD_TABLE = {
+        self._QUAD_TABLE: dict[ICInstruction, ICInfo] = {
             ICInstruction.ADDU8: ICInfo(3, Bits8.add8),
             ICInstruction.ADDI8: ICInfo(3, Bits8.add8),
             ICInstruction.ADDI16: ICInfo(3, Bits16.add16),