diff --git a/build.sh b/build.sh
index 01c44ca..eb49bad 100644
--- a/build.sh
+++ b/build.sh
@@ -207,30 +207,8 @@ for target in "${targets[@]}"; do
 		patch --directory="${toolchain_directory}/${triple}" --strip='1' --input="${workdir}/patches/linux_pim.patch"
 	fi
 	
-	cd "${toolchain_directory}/${triple}/include"
-	
 	if ! (( is_native )); then
-		CC="${triple}-gcc" python "${workdir}/tools/make_builtins.py"
-		
-		if [ -f './builtin_ctype.h' ]; then
-			echo '#include <builtin_ctype.h>' >> './ctype.h'
-		fi
-		
-		if [ -f './builtin_math.h' ]; then
-			echo '#include <builtin_math.h>' >> './math.h'
-		fi
-		
-		if [ -f './builtin_stdio.h' ]; then
-			echo '#include <builtin_stdio.h>' >> './stdio.h'
-		fi
-		
-		if [ -f './builtin_complex.h' ]; then
-			echo '#include <builtin_complex.h>' >> './complex.h'
-		fi
-		
-		if [ -f './builtin_stdlib.h' ]; then
-			echo '#include <builtin_stdlib.h>' >> './stdlib.h'
-		fi
+		C_INCLUDE_PATH="${toolchain_directory}/${triple}/include" CC="${triple}-gcc" python "${workdir}/tools/make_builtins.py"
 	fi
 	
 	[ -d "${binutils_directory}/build" ] || mkdir "${binutils_directory}/build"
diff --git a/tools/builtin_symbols.json b/tools/builtin_symbols.json
index 782064b..ef680da 100644
--- a/tools/builtin_symbols.json
+++ b/tools/builtin_symbols.json
@@ -445,7 +445,7 @@
 	},
 	{
 		"name": "imaxabs",
-		"header": "ctype"
+		"header": "inttypes"
 	},
 	{
 		"name": "isblank",
@@ -453,7 +453,7 @@
 	},
 	{
 		"name": "iswblank",
-		"header": "ctype"
+		"header": "wctype"
 	},
 	{
 		"name": "lgammaf",
diff --git a/tools/make_builtins.py b/tools/make_builtins.py
index 559a63b..c0031bd 100644
--- a/tools/make_builtins.py
+++ b/tools/make_builtins.py
@@ -2,8 +2,19 @@
 import os
 import subprocess
 import tempfile
+import shutil
+
+headers = (
+	"math",
+	"stdio",
+	"complex",
+	"stdlib",
+	"ctype",
+	"wctype",
+	"inttypes"
+)
 
-source = """
+source = """\
 #include <%s.h>
 
 int main(void) {
@@ -12,7 +23,7 @@
 }
 """
 
-destination = """
+destination = """\
 #if !defined(BUILTIN_COMPAT_%s_H)
 #define BUILTIN_COMPAT_%s_H
 %s
@@ -35,12 +46,16 @@ def __init__(self):
 		self.complex = []
 		self.stdlib = []
 		self.ctype = []
+		self.wctype = []
+		self.inttypes = []
 
 content = None
 
 cc = os.getenv(key = "CC")
+c_include_path = os.getenv(key = "C_INCLUDE_PATH")
 
 assert cc is not None
+assert c_include_path is not None
 
 def check_symbols_exists(symbol):
 	
@@ -51,7 +66,7 @@ def check_symbols_exists(symbol):
 	with open(file = temporary_file, mode = "w") as file:
 		file.write(text)
 	
-	process = subprocess.run([cc, "-w", "-fno-builtin", temporary_file, "-o", "%s.o" % temporary_file])
+	process = subprocess.run([cc, "-std=c23", "-w", "-fno-builtin", temporary_file, "-o", "%s.o" % temporary_file])
 	
 	return process.returncode == 0
 
@@ -69,7 +84,11 @@ def dump_builtins(builtins, name):
 	for item in items:
 		s += ("\n#define %s __builtin_%s" % (item, item))
 	
-	dump = destination % (name.upper(), name.upper(), s)
+	dump = destination % (
+		name.upper(),
+		name.upper(),
+		s
+	)
 	
 	with open(file = "builtin_%s.h" % (name), mode = "w") as file:
 		file.write(dump)
@@ -95,8 +114,23 @@ def dump_builtins(builtins, name):
 	items = getattr(builtins, header)
 	items.append(name)
 
-dump_builtins(builtins, "math")
-dump_builtins(builtins, "stdio")
-dump_builtins(builtins, "complex")
-dump_builtins(builtins, "stdlib")
-dump_builtins(builtins, "ctype")
+for name in headers:
+	dump_builtins(builtins = builtins, name = name)
+	
+	src = "builtin_%s.h" % (name)
+	dst = os.path.join(c_include_path, "%s.h" % (name))
+	
+	if not os.path.exists(path = src):
+		continue
+	
+	print("- Modifying '%s'" % (dst))
+	
+	with open(file = dst, mode = "a+") as file:
+		file.write("\n\n#include <%s>" % (src))
+	
+	dst = os.path.join(c_include_path, src)
+	
+	if os.path.exists(path = dst):
+		os.remove(dst)
+	
+	shutil.move(src = src, dst = dst)