diff --git a/src/layers/normalise.jl b/src/layers/normalise.jl
index b9f7a86c..e48d26fb 100644
--- a/src/layers/normalise.jl
+++ b/src/layers/normalise.jl
@@ -133,7 +133,7 @@ function (BN::BatchNorm)(x)
     # update moving mean/std
     mtm = data(convert(T, BN.momentum))
     BN.μ = (1 - mtm) .* BN.μ .+ mtm .* reshape(data(μ), :)
-    BN.σ² = (1 - mtm) .* BN.σ² .+ mtm .* reshape(data(σ²), :) .* m ./ (m - 1)
+    BN.σ² = (1 - mtm) .* BN.σ² .+ (mtm * m / (m - 1)) .* reshape(data(σ²), :)
   end
 
   let λ = BN.λ