diff --git a/src/compiler/loops.jl b/src/compiler/loops.jl
index 33f38cdd..ce4bd5ed 100644
--- a/src/compiler/loops.jl
+++ b/src/compiler/loops.jl
@@ -29,19 +29,30 @@ struct SeqModel
   steps::Int
 end
 
-runseq(f, xs::Tuple...) = f(xs...)
-runseq(f, xs::AbstractArray...) = stack(f(map(x -> (unstack(x,2)...,), xs)...), 2)
-runseq(f, xs::Batch{<:Seq}...) = convert(Batch{Seq}, runseq(f, rawbatch.(xs)...))
-runseq(f, xs) = runseq(f, (xs...,))
+seqtuple(x, n) = x
+seqtuple(xs::Tuple, n) = seqtuple.(xs, n)
 
-function (m::SeqModel)(x)
-  runseq(x) do x
-    @assert length(x) == m.steps "Expected seq length $(m.steps), got $(size(x, 2))"
-    m.model(x)
-  end
+seqtuple(xs::AbstractArray, n) =
+  ndims(xs) < 3 ? xs :
+  n ≠ 0 && size(xs, 2) ≠ n ? error("Expecting sequence length $n, got $(size(xs, 2))") :
+  (unstack(xs, 2)...)
+
+seqtuple(xs::Batch{<:Seq}, n) = seqtuple(rawbatch(xs), n)
+
+reseq(x) = x
+reseq(x::Tuple{}) = ()
+reseq(xs::Tuple) = all(isa.(xs, AbstractArray) .& (ndims.(xs) .≥ 2)) ? stack(xs, 2) : reseq.(xs)
+
+function (m::SeqModel)(xs...)
+  xs = seqtuple(xs, m.steps)
+  reseq(m.model(xs...))
 end
 
-back!(m::SeqModel, Δ, x) = (runseq((Δ, x) -> back!(m.model, Δ, x)[1], Δ, x),)
+function back!(m::SeqModel, args...)
+  args = seqtuple(args, 0)
+  # TODO: reseq
+  back!(m.model, args...)
+end
 
 update!(m::SeqModel, η) = update!(m.model, η)
 
diff --git a/src/training.jl b/src/training.jl
index 70088444..62a34c46 100644
--- a/src/training.jl
+++ b/src/training.jl
@@ -30,7 +30,7 @@ function train!(m, train; cb = [],
     @progress for e in 1:epoch
       info("Epoch $e")
       @cb for (x, y) in train
-        x, y = tobatch.((x, y))
+        x, y = mapt(tobatch, (x, y))
         ŷ = m(x)
         any(isnan, ŷ) && error("NaN")
         Δ = back!(loss, 1, ŷ, y)