diff --git a/src/Flux.jl b/src/Flux.jl
index df4b1636..7671ddd2 100644
--- a/src/Flux.jl
+++ b/src/Flux.jl
@@ -12,7 +12,7 @@ export Chain, Dense, RNN, LSTM, Dropout, LayerNorm,
   param, params, mapleaves
 
 using NNlib
-export σ, relu, leakyrelu, elu, swish, softmax
+export σ, sigmoid, relu, leakyrelu, elu, swish, softmax
 
 include("tracker/Tracker.jl")
 using .Tracker
diff --git a/src/onehot.jl b/src/onehot.jl
index f8061063..f94fb93e 100644
--- a/src/onehot.jl
+++ b/src/onehot.jl
@@ -42,7 +42,14 @@ function onehot(l, labels)
   OneHotVector(i, length(labels))
 end
 
-onehotbatch(ls, labels) = OneHotMatrix(length(labels), [onehot(l, labels) for l in ls])
+function onehot(l, labels, unk)
+  i = findfirst(labels, l)
+  i > 0 || return onehot(unk, labels)
+  OneHotVector(i, length(labels))
+end
+
+onehotbatch(ls, labels, unk...) =
+  OneHotMatrix(length(labels), [onehot(l, labels, unk...) for l in ls])
 
 argmax(y::AbstractVector, labels = 1:length(y)) =
   labels[findfirst(y, maximum(y))]
diff --git a/src/tracker/Tracker.jl b/src/tracker/Tracker.jl
index 57bdc447..376cc617 100644
--- a/src/tracker/Tracker.jl
+++ b/src/tracker/Tracker.jl
@@ -40,7 +40,7 @@ TrackedArray(x::AbstractArray) = TrackedArray(Call(nothing), x, zeros(x))
 
 isleaf(x::TrackedArray) = x.f == Call(nothing)
 
-param(xs) = TrackedArray(AbstractFloat.(xs))
+param(xs) = TrackedArray(map(x -> AbstractFloat(x), xs))
 param(xs::Real) = param(fill(xs))
 
 istracked(x::TrackedArray) = true