diff --git a/src/io.jl b/src/io.jl
index d77b6ff7d..ac37a8d84 100644
--- a/src/io.jl
+++ b/src/io.jl
@@ -259,10 +259,10 @@ Construct a data provider from `NDArray` or Julia Arrays.
 TODO: remove `data_padding` and `label_padding`, and implement rollover that copies
 the last or first several training samples to feed the padding.
 """
-mutable struct ArrayDataProvider{T,N,S,M} <: AbstractDataProvider
+mutable struct ArrayDataProvider{T,N} <: AbstractDataProvider
   data_arrays   :: Vector{Array{T,N}}
   data_names    :: Vector{Symbol}
-  label_arrays  :: Vector{Array{S,M}}
+  label_arrays
   label_names   :: Vector{Symbol}
   batch_size    :: Int
   sample_count  :: Int
@@ -270,8 +270,8 @@ mutable struct ArrayDataProvider{T,N,S,M} <: AbstractDataProvider
   data_padding  :: MX_float
   label_padding :: MX_float
 
-  data_batch    :: Vector{NDArray{T,N}}
-  label_batch   :: Vector{NDArray{S,M}}
+  data_batch
+  label_batch
 end
 
 # Julia's type system is sometimes very frustrating. You cannot specify a function