diff --git a/src/utils.jl b/src/utils.jl
index 9bad3760..1bdfe456 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -10,8 +10,8 @@ zeros(dims...) = Base.zeros(Float32, dims...)
 
 unsqueeze(xs, dim) = reshape(xs, (size(xs)[1:dim-1]..., 1, size(xs)[dim:end]...))
 
-stack(xs, dim) = cat(dim, unsqueeze.(xs, dim)...)
-unstack(xs, dim) = [slicedim(xs, dim, i) for i = 1:size(xs, dim)]
+stack(xs, dim) = cat(unsqueeze.(xs, dim)..., dims=dim)
+unstack(xs, dim) = [copy(selectdim(xs, dim, i)) for i in 1:size(xs, dim)]
 
 """
     chunk(xs, n)