diff --git a/src/layers/normalise.jl b/src/layers/normalise.jl
index 59b39ca7..2876cdd7 100644
--- a/src/layers/normalise.jl
+++ b/src/layers/normalise.jl
@@ -136,7 +136,7 @@ function (BN::BatchNorm)(x)
   dims = length(size(x))
   channels = size(x, dims-1)
   affine_shape = ntuple(i->i == ndims(x) - 1 ? size(x, i) : 1, ndims(x))
-  m = prod(size(x)[1:end-2]) * size(x)[end]
+  m = trunc(Int, prod(size(x))/channels)
   γ = reshape(BN.γ, affine_shape...)
   β = reshape(BN.β, affine_shape...)
   if !istraining()