diff --git a/melamine/shred.py b/melamine/shred.py
index c6c3523..2f9ba2a 100644
--- a/melamine/shred.py
+++ b/melamine/shred.py
@@ -9,7 +9,7 @@ from .classes import ShredDir
 from .classes import ShredFile
 from .logs import logger
 
-IGNORE_GLOBAL = set("/proc", "/dev", "/sys")
+IGNORE_GLOBAL = ("/proc", "/dev", "/sys")
 
 
 async def main(job: argparse.Namespace) -> bool: