diff --git a/bypy/sources.json b/bypy/sources.json
index 292c720576..e0b2c6d05c 100644
--- a/bypy/sources.json
+++ b/bypy/sources.json
@@ -67,8 +67,8 @@
     {
         "name": "zlib",
         "unix": {
-            "filename": "zlib-1.3.tar.xz",
-            "hash": "sha256:8a9ba2898e1d0d774eca6ba5b4627a11e5588ba85c8851336eb38de4683050a7",
+            "filename": "zlib-1.3.1.tar.xz",
+            "hash": "sha256:38ef96b8dfe510d42707d9c781877914792541133e1870841463bfa73f883e32",
             "urls": ["https://zlib.net/{filename}"]
         }
     },