diff --git a/caricari/private.py b/caricari/private.py
index f8e1423..44fb8a7 100644
--- a/caricari/private.py
+++ b/caricari/private.py
@@ -58,11 +58,13 @@ def normalize_filename(filename: str):
     'ciao'
     >>> normalize_filename("Hello, 42 worlds!")
     'Hello42worlds'
+    >>> normalize_filename("Hey, do you want to hear my story?" * 10)
+    'HeydoyouwanttohearmystoryHeydo'
     """
     return "".join(
             c for c in filename
             if c.isalnum() or c in '-_'
-            )
+            )[:40]
 
 @app.post("/upload")
 async def upload(