diff --git a/requirements.in b/requirements.in
index 985caa8..d9f53ff 100644
--- a/requirements.in
+++ b/requirements.in
@@ -2,3 +2,4 @@ beautifulsoup4
 pypdf
 aiohttp
 aiohttp_requests
+cython>=3.0.0
diff --git a/requirements.txt b/requirements.txt
index 402e516..514d9d8 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -26,6 +26,8 @@ cffi==1.15.1
     # via pycares
 charset-normalizer==2.1.1
     # via aiohttp
+cython==3.0.0
+    # via -r requirements.in
 frozenlist==1.3.3
     # via
     #   aiohttp