diff --git a/src/arch/z80/backend/common.py b/src/arch/z80/backend/common.py
index 933b12b08..07a1dd01b 100644
--- a/src/arch/z80/backend/common.py
+++ b/src/arch/z80/backend/common.py
@@ -34,6 +34,7 @@ class DataType(StrEnum):
     i32 = "i32"
     f16 = "f16"
     f = "f"
+    str = "str"
 
 
 # Handy constants, to not having to type long names :-)
@@ -46,7 +47,7 @@ class DataType(StrEnum):
 I32_t: Final[DataType] = DataType.i32
 F16_t: Final[DataType] = DataType.f16
 F_t: Final[DataType] = DataType.f
-
+STR_t: Final[DataType] = DataType.str
 
 # Internal data types definition, with its size in bytes, or -1 if it is variable (string)
 # Compound types are only arrays, and have the t
@@ -297,32 +298,6 @@ def get_bytes_size(elements: list[str]) -> int:
     return len(get_bytes(elements))
 
 
-def to_bool(stype: DataType) -> list[str]:
-    """Returns the instruction sequence for converting the number given number (in the stack)
-    to boolean (just 0 (False) or non-zero (True))."""
-
-    if stype in (U8_t, I8_t):
-        return []
-
-    if stype in (U16_t, I16_t):
-        return [
-            "ld a, h" "or l",
-        ]
-
-    if stype in (U32_t, I32_t, F16_t):
-        return ["ld a, h" "or l" "or d", "or e,"]
-
-    if stype == F_t:
-        return [
-            "or b",
-            "or c",
-            "or d",
-            "or e",
-        ]
-
-    raise NotImplementedError(f"type conversion from {stype} to bool is undefined")
-
-
 def normalize_boolean() -> list[str]:
     if OPTIONS.opt_strategy == OptimizationStrategy.Size:
         return [runtime_call(RuntimeLabel.NORMALIZE_BOOLEAN)]
diff --git a/src/arch/z80/backend/generic.py b/src/arch/z80/backend/generic.py
index 882e49739..691923d1d 100644
--- a/src/arch/z80/backend/generic.py
+++ b/src/arch/z80/backend/generic.py
@@ -24,7 +24,6 @@
     get_bytes_size,
     new_ASMID,
     runtime_call,
-    to_bool,
     to_byte,
     to_fixed,
     to_float,
@@ -365,8 +364,6 @@ def _cast(ins: Quad):
         output.extend(to_fixed(tA))
     elif tB == "f":
         output.extend(to_float(tA))
-    elif tB == "bool":
-        output.extend(to_bool(tA))
     else:
         raise exception.GenericError("Internal error: invalid typecast from %s to %s" % (tA, tB))
 
diff --git a/src/arch/z80/visitor/translator_inst_visitor.py b/src/arch/z80/visitor/translator_inst_visitor.py
index c853744af..04c100e11 100644
--- a/src/arch/z80/visitor/translator_inst_visitor.py
+++ b/src/arch/z80/visitor/translator_inst_visitor.py
@@ -2,7 +2,7 @@
 from src.api.debug import __DEBUG__
 from src.arch.interface.quad import Quad
 from src.arch.z80.backend import Backend
-from src.arch.z80.backend.common import BOOL_t, F16_t, F_t, I8_t, I16_t, I32_t, U8_t, U16_t, U32_t
+from src.arch.z80.backend.common import BOOL_t, F16_t, F_t, I8_t, I16_t, I32_t, STR_t, U8_t, U16_t, U32_t
 from src.ast import NodeVisitor
 from src.symbols import sym as symbols
 
@@ -30,7 +30,7 @@ def TSUFFIX(type_: TYPE | symbols.TYPEREF | symbols.BASICTYPE) -> str:
             TYPE.ulong: U32_t,
             TYPE.fixed: F16_t,
             TYPE.float: F_t,
-            TYPE.string: "str",
+            TYPE.string: STR_t,
             TYPE.boolean: BOOL_t,
         }
 
diff --git a/src/zxbpp/base_pplex.py b/src/zxbpp/base_pplex.py
index 274f474a0..678ed3376 100644
--- a/src/zxbpp/base_pplex.py
+++ b/src/zxbpp/base_pplex.py
@@ -9,7 +9,7 @@
 
 import os
 import sys
-from collections.abc import Iterable
+from collections.abc import Callable, Iterable
 from dataclasses import dataclass
 from enum import Enum, unique
 
@@ -88,6 +88,10 @@ def __init__(
         for macro_name, macro_func in self.builtin_macros.items():
             self.defines_table[macro_name] = BuiltinMacro(macro_name=macro_name, func=macro_func)
 
+    def set_macro(self, macro_name: str, func: Callable[[str], str]) -> None:
+        assert self.defines_table is not None
+        self.defines_table[macro_name] = func
+
     def put_current_line(self, prefix: str = "", suffix: str = "") -> str:
         """Returns line and file for include / end of include sequences."""
         assert self.lex is not None
diff --git a/src/zxbpp/prepro/builtinmacro.py b/src/zxbpp/prepro/builtinmacro.py
index 077de2c0d..b6a44ccbd 100644
--- a/src/zxbpp/prepro/builtinmacro.py
+++ b/src/zxbpp/prepro/builtinmacro.py
@@ -1,3 +1,5 @@
+from collections.abc import Callable
+
 from src.zxbpp import prepro
 
 from .id_ import ID
@@ -7,12 +9,12 @@
 class BuiltinMacro(ID):
     """A call to a builtin macro like __FILE__ or __LINE__
     Every time the macro() is called, the macro returns
-    it value.
+    its value.
     """
 
-    def __init__(self, macro_name: str, func):
+    def __init__(self, macro_name: str, func: Callable[[MacroCall | None], str]):
         super().__init__(fname="", lineno=0, id_=macro_name)
         self.func = func
 
-    def __call__(self, symbolTable: "prepro.DefinesTable" = None, macro: MacroCall = None) -> str:
+    def __call__(self, symbolTable: prepro.DefinesTable | None = None, macro: MacroCall | None = None) -> str:
         return self.func(macro)
diff --git a/src/zxbpp/zxbpp.py b/src/zxbpp/zxbpp.py
index a23ffdc42..ff03b11b8 100755
--- a/src/zxbpp/zxbpp.py
+++ b/src/zxbpp/zxbpp.py
@@ -112,8 +112,7 @@ def reset_id_table():
         ID_TABLE.define(name, value=val, lineno=0)
 
     for macro_name, macro_func in LEXER.builtin_macros.items():
-        # FIXME
-        LEXER.defines_table[macro_name] = BuiltinMacro(macro_name=macro_name, func=macro_func)  # type: ignore[index]
+        LEXER.set_macro(macro_name, BuiltinMacro(macro_name=macro_name, func=macro_func))
 
 
 def init():