diff --git a/src/jit/shapes.jl b/src/jit/shapes.jl
index 1443c4f0..45998b0a 100644
--- a/src/jit/shapes.jl
+++ b/src/jit/shapes.jl
@@ -8,6 +8,7 @@ VecShape{T} = Shape{T,1}
 MatShape{T} = Shape{T,2}
 
 Shape{T}(dims::Vararg{Integer,N}) where {T,N} = Shape{T,N}(dims)
+Shape{T}(dims::NTuple{N,Integer}) where {T,N} = Shape{T,N}(dims)
 
 Base.size(s::Shape) = s.dims
 Base.size(s::Shape, n) = s.dims[n]
@@ -22,7 +23,7 @@ function Base.show(io::IO, s::Shape{T}) where T
   print(io, ")")
 end
 
-shape(x) = typeof(x)
+shape(x) = x
 shape(x::Shape) = x
 shape(x::Tuple) = shape.(x)
 shape(x::AbstractArray) = Shape{eltype(x)}(size(x)...)
diff --git a/src/jit/trace.jl b/src/jit/trace.jl
index 565d7724..01bf0afc 100644
--- a/src/jit/trace.jl
+++ b/src/jit/trace.jl
@@ -53,9 +53,12 @@ struct Compiled{F,T<:Tuple}
   params::T
 end
 
-(c::Compiled)(args...) =
-  Tracker.track(Tracker.Call(c, args...),
-                c.func(Tracker.data.(c.params), args...))
+# TODO when we support derivatives
+# (c::Compiled)(args...) =
+#   Tracker.track(Tracker.Call(c, args...),
+#                 c.func(Tracker.data.(c.params), args...))
+
+(c::Compiled)(args...) = c.func(Tracker.data.(c.params), Tracker.data.(args)...)
 
 Base.show(io::IO, c::Compiled) = print(io, "Compiled(", c.model, ")")