diff --git a/saas_web.py b/saas_web.py
index 63265e9..4c123b8 100644
--- a/saas_web.py
+++ b/saas_web.py
@@ -114,7 +114,8 @@ async def require_api_key(request: Request, call_next):
     if configured_keys and not (request.method == "GET" and request.url.path == "/"):
         provided_key = request.headers.get("x-api-key", "")
         if not any(
-            hmac.compare_digest(provided_key, key) for key in configured_keys
+            hmac.compare_digest(provided_key.encode("utf-8"), key.encode("utf-8"))
+            for key in configured_keys
         ):
             return JSONResponse(
                 status_code=401,
diff --git a/tests/test_saas_web.py b/tests/test_saas_web.py
index 3b57e03..0e19dd7 100644
--- a/tests/test_saas_web.py
+++ b/tests/test_saas_web.py
@@ -707,6 +707,29 @@ def test_missing_header_rejected_when_keys_configured(self):
         self.assertEqual(response.json(), {"error": "Invalid or missing API key"})
         self.assertNotIn("secret-key", response.text)
 
+    def test_non_ascii_key_does_not_crash(self):
+        with patch.dict(os.environ, {"CODEC_CARVER_API_KEYS": "secret-key"}):
+            # Using raw ASGI scope to bypass HTTPX ASCII limitations on headers
+            import fastapi
+            import asyncio
+            import json
+            import saas_web
+            scope = {
+                "type": "http",
+                "method": "POST",
+                "path": "/shrink",
+                "headers": [(b"x-api-key", "한글".encode("utf-8"))]
+            }
+            request = fastapi.Request(scope)
+
+            async def dummy_call_next(req):
+                return fastapi.responses.JSONResponse({"success": True})
+
+            response = asyncio.run(saas_web.require_api_key(request, dummy_call_next))
+
+            self.assertEqual(response.status_code, 401)
+            self.assertEqual(json.loads(response.body), {"error": "Invalid or missing API key"})
+
     def test_wrong_key_rejected(self):
         with patch.dict(os.environ, {"CODEC_CARVER_API_KEYS": "secret-key"}):
             response = self._post_shrink(headers={"X-API-Key": "wrong-key"})