diff --git a/llmfoundry/optim/scheduler.py b/llmfoundry/optim/scheduler.py
index 9d3cb6be02..5598db28a1 100644
--- a/llmfoundry/optim/scheduler.py
+++ b/llmfoundry/optim/scheduler.py
@@ -16,23 +16,19 @@
 
 def _raise_if_units_dont_match(time: Union[str, Time], t_max: Union[str, Time],
                                name: str) -> None:
-    time = Time.from_input(time)
-    t_max = Time.from_input(t_max)
+    new_time = Time.from_input(time)
+    new_t_max = Time.from_input(t_max)
 
-    assert not isinstance(time, str) and not isinstance(t_max, str)
-
-    if time.unit != t_max.unit:
+    if new_time.unit != new_t_max.unit:
         raise ValueError(
-            f'{name} (unit {time.unit=}) must match max_duration unit ({t_max.unit=}).'
+            f'{name} (unit {new_time.unit=}) must match max_duration unit ({new_t_max.unit=}).'
         )
 
 
 def _raise_if_units_dur(time: Union[str, Time], name: str) -> None:
-    time = Time.from_input(time)
-
-    assert not isinstance(time, str)
+    new_time = Time.from_input(time)
 
-    if time.unit == TimeUnit('dur'):
+    if new_time.unit == TimeUnit('dur'):
         raise ValueError(f'{name} cannot be in units of "dur".')