diff --git a/tools/build/main.py b/tools/build/main.py
index a19e6ad..0d7aa47 100644
--- a/tools/build/main.py
+++ b/tools/build/main.py
@@ -54,6 +54,10 @@ MetaToml = TypedDict(
 )
 
 
+def sanitize_file_name(file: str) -> str:
+	return file.replace("?", "")
+
+
 def read_meta_toml(file: Path) -> MetaToml:
 	with file.open("rb") as f:
 		base = tomllib.load(f)
@@ -132,6 +136,7 @@ def build_typst(source_dir: Path, out_subdir: Path) -> IndexEntry | None:
 	out = OUT_DIR / out_subdir
 	out.mkdir(parents=True, exist_ok=True)
 
+	file_name = sanitize_file_name(f"{meta['title']}.pdf")
 	res = subprocess.run(
 		[
 			TYPST_PATH,
@@ -140,7 +145,7 @@ def build_typst(source_dir: Path, out_subdir: Path) -> IndexEntry | None:
 			"main.typ",
 			"--input",
 			"show_solutions=false",
-			f"{out}/{meta['title']}.pdf",
+			f"{out}/{file_name}",
 		],
 		cwd=source_dir,
 		stdout=subprocess.PIPE,
@@ -153,13 +158,14 @@ def build_typst(source_dir: Path, out_subdir: Path) -> IndexEntry | None:
 	# Build solutions
 	if meta["publish_solutions"]:
 		log(f"Building typst (solutions): {source_dir}")
+		file_name = sanitize_file_name(f"{meta['title']}.sols.pdf")
 		res = subprocess.run(
 			[
 				TYPST_PATH,
 				"compile",
 				"--ignore-system-fonts",
 				"main.typ",
-				f"{out}/{meta['title']}.sols.pdf",
+				f"{out}/{file_name}",
 			],
 			cwd=source_dir,
 			stdout=subprocess.PIPE,
@@ -213,8 +219,9 @@ def build_xetex(source_dir: Path, out_subdir: Path) -> IndexEntry | None:
 		stderr=subprocess.PIPE,
 	)
 
+	file_name = sanitize_file_name(f"{meta['title']}.pdf")
 	try:
-		shutil.copy(source_dir / "main.pdf", f"{out}/{meta['title']}.pdf")
+		shutil.copy(source_dir / "main.pdf", f"{out}/{file_name}")
 	except Exception as e:
 		log(f"Error: {e}")
 		log_error(res)
@@ -236,8 +243,9 @@ def build_xetex(source_dir: Path, out_subdir: Path) -> IndexEntry | None:
 			stderr=subprocess.PIPE,
 		)
 
+		file_name = sanitize_file_name(f"{meta['title']}.sols.pdf")
 		try:
-			shutil.copy(source_dir / "main.pdf", f"{out}/{meta['title']}.sols.pdf")
+			shutil.copy(source_dir / "main.pdf", f"{out}/{file_name}")
 		except Exception as e:
 			log(f"Error: {e}")
 			log_error(res)