diff --git a/tunix/rl/utils.py b/tunix/rl/utils.py
index 1888368f7..13167c236 100644
--- a/tunix/rl/utils.py
+++ b/tunix/rl/utils.py
@@ -34,7 +34,7 @@
 
 def is_positive_integer(value: int | None, name: str):
   """Checks if the value is positive."""
-  if value is not None and (not value.is_integer() or value <= 0):
+  if value is not None and (not isinstance(value, int) or value <= 0):
     raise ValueError(f"{name} must be a positive integer. Got: {value}")