diff --git a/ttlcollections/structures.py b/ttlcollections/structures.py
index d60d980..cfe7f4d 100644
--- a/ttlcollections/structures.py
+++ b/ttlcollections/structures.py
@@ -129,7 +129,7 @@ class TTLStack:
 
         self.timer = timer
         self.ttl = ttl
-        self.size = size
+        self.size = size if size else math.inf
         self._stack = deque()
 
     def push(self, element, ttl: int = 0):