diff --git a/wandb_preempt/checkpointer.py b/wandb_preempt/checkpointer.py
index 103e41a..14eae69 100644
--- a/wandb_preempt/checkpointer.py
+++ b/wandb_preempt/checkpointer.py
@@ -35,7 +35,7 @@ def __init__(
         self,
         run_id: str,
         model: Module,
-        optimizer: Optimizer,
+        optimizer: Union[Optimizer, None],
         lr_scheduler: Optional[LRScheduler] = None,
         scaler: Optional[GradScaler] = None,
         savedir: str = "checkpoints",
@@ -46,7 +46,10 @@ def __init__(
         Args:
             run_id: A unique identifier for this run.
             model: The model that is trained and checkpointed.
-            optimizer: The optimizer that is used for training and checkpointed.
+            optimizer: The optimizer that is used for training and should be
+                checkpointed. Use `None` to explicitly ignore the optimizer. This can
+                be useful if your optimizer does not implement `.state_dict` and
+                `.load_state_dict`.
             lr_scheduler: The learning rate scheduler that is used for training. If
                 `None`, no learning rate scheduler is assumed. Default: `None`.
             scaler: The gradient scaler that is used when training in mixed precision.
@@ -151,12 +154,13 @@ def save_checkpoint(self, extra_info: Dict) -> None:
         }
         data = {
             "model": self.model.state_dict(),
-            "optimizer": self.optimizer.state_dict(),
             "rng_states": rng_states,
             "checkpoint_step": self.step_count,
             "resumes": self.num_resumes,
             "extra_info": extra_info,
         }
+        if self.optimizer is not None:
+            data["optimizer"] = self.optimizer.state_dict()
         if self.lr_scheduler is not None:
             data["lr_scheduler"] = self.lr_scheduler.state_dict()
         if self.scaler is not None:
@@ -209,8 +213,9 @@ def load_latest_checkpoint(
         data = load(loadpath, weights_only=weights_only, **kwargs)
         self.maybe_print("Loading model.")
         self.model.load_state_dict(data["model"])
-        self.maybe_print("Loading optimizer.")
-        self.optimizer.load_state_dict(data["optimizer"])
+        if self.optimizer is not None:
+            self.maybe_print("Loading optimizer.")
+            self.optimizer.load_state_dict(data["optimizer"])
         if self.lr_scheduler is not None:
             self.maybe_print("Loading lr scheduler.")
             self.lr_scheduler.load_state_dict(data["lr_scheduler"])