diff --git a/torchcast/exp_smooth/exp_smooth.py b/torchcast/exp_smooth/exp_smooth.py
index d47ea33..cf58d24 100644
--- a/torchcast/exp_smooth/exp_smooth.py
+++ b/torchcast/exp_smooth/exp_smooth.py
@@ -51,6 +51,9 @@ def predict(self,
                 cov: Tensor,
                 mask: Tensor,
                 kwargs: Dict[str, Tensor]) -> Tuple[Tensor, Tensor]:
+        if mask.all():
+            mask = slice(None)
+
         F = kwargs['F'][mask]
 
         new_mean = update_tensor(mean, new=(F @ mean[mask].unsqueeze(-1)).squeeze(-1), mask=mask)
diff --git a/torchcast/internals/utils.py b/torchcast/internals/utils.py
index ae4afc1..8034e4a 100644
--- a/torchcast/internals/utils.py
+++ b/torchcast/internals/utils.py
@@ -6,7 +6,7 @@
 import numpy as np
 
 
-def update_tensor(orig: torch.Tensor, new: torch.Tensor, mask: torch.Tensor) -> torch.Tensor:
+def update_tensor(orig: torch.Tensor, new: torch.Tensor, mask: Optional[Union[slice, torch.Tensor]]) -> torch.Tensor:
     """
     In some cases we will want to save compute by only performing operations on a subset of a tensor, leaving the other
     elements as-is. In this case we'd need:
@@ -28,13 +28,16 @@ def update_tensor(orig: torch.Tensor, new: torch.Tensor, mask: torch.Tensor) ->
     :return: If ``mask`` is all True, returns ``new`` (not a copy). Otherwise, returns a new tensor with the same shape
      as ``orig`` where the elements in ``mask`` are replaced with the elements in ``new``.
     """
-    if mask.all():
+    if isinstance(mask, slice) and not mask.start and not mask.stop and not mask.step:
+        mask = None
+    if mask is None or mask.all():
         return new
     else:
         out = orig.clone()
         out[mask] = new
         return out
 
+
 def transpose_last_dims(x: torch.Tensor) -> torch.Tensor:
     args = list(range(len(x.shape)))
     args[-2], args[-1] = args[-1], args[-2]
diff --git a/torchcast/kalman_filter/kalman_filter.py b/torchcast/kalman_filter/kalman_filter.py
index a639ed0..fc21a67 100644
--- a/torchcast/kalman_filter/kalman_filter.py
+++ b/torchcast/kalman_filter/kalman_filter.py
@@ -31,6 +31,8 @@ def predict(self,
                 cov: Tensor,
                 mask: Tensor,
                 kwargs: Dict[str, Tensor]) -> Tuple[Tensor, Tensor]:
+        if mask.all():
+            mask = slice(None)
         F = kwargs['F'][mask]
         Q = kwargs['Q'][mask]