diff --git a/src/tracker/numeric.jl b/src/tracker/numeric.jl
index 73c63029..65cab8b8 100644
--- a/src/tracker/numeric.jl
+++ b/src/tracker/numeric.jl
@@ -5,15 +5,17 @@ function gradient(f, xs::AbstractArray...)
 end
 
 function ngradient(f, xs::AbstractArray...)
-  y = f(xs...)
   grads = zeros.(xs)
   for (x, Δ) in zip(xs, grads)
     for i in 1:length(x)
       δ = sqrt(eps())
-      tmp, x[i] = x[i], x[i]+δ
-      y′ = f(xs...)
+      tmp = x[i]
+      x[i] = tmp - δ/2
+      y1 = f(xs...)
+      x[i] = tmp + δ/2
+      y2 = f(xs...)
       x[i] = tmp
-      Δ[i] = (y′-y)/δ
+      Δ[i] = (y2-y1)/δ
     end
   end
   return grads
diff --git a/test/tracker.jl b/test/tracker.jl
index 1e64b23a..258e1af4 100644
--- a/test/tracker.jl
+++ b/test/tracker.jl
@@ -11,10 +11,12 @@ gradtest(f, dims...) = gradtest(f, rand.(dims)...)
 
 @test gradtest(x -> sin.(sum(x, (2, 3))), (3,4,5))
 
-gradtest(x -> softmax(x).*(1:3), 3)
-gradtest(x -> softmax(x).*(1:3), (3,5))
+@test gradtest(x -> softmax(x).*(1:3), 3)
+@test gradtest(x -> softmax(x).*(1:3), (3,5))
 
-gradtest(Flux.mse, rand(5,5), rand(5, 5))
-gradtest(Flux.logloss, rand(5,5), rand(5, 5))
+@test gradtest(Flux.mse, rand(5,5), rand(5, 5))
+@test gradtest(Flux.logloss, rand(5,5), rand(5, 5))
+
+@test gradtest(x -> x', rand(5))
 
 end