diff --git a/src/tracker/Tracker.jl b/src/tracker/Tracker.jl
index 96ed3bcf..4b7771c5 100644
--- a/src/tracker/Tracker.jl
+++ b/src/tracker/Tracker.jl
@@ -28,6 +28,7 @@ mutable struct Tracked{T}
 end
 
 Tracked(f::Call, x) = Tracked{typeof(x)}(f, x)
+Tracked(f::Call, x, Δ) = Tracked{typeof(x)}(f, x, Δ)
 
 track(f::Call, x) = Tracked(f, x)
 track(f::Call) = track(f, f())
diff --git a/src/tracker/scalar.jl b/src/tracker/scalar.jl
index 3f38d9f0..ab003f90 100644
--- a/src/tracker/scalar.jl
+++ b/src/tracker/scalar.jl
@@ -2,11 +2,11 @@ struct TrackedNumber{T<:Number} <: Number
   tracker::Tracked{T}
 end
 
-TrackedNumber(x::Number) = TrackedNumber(Tracked(Call(nothing), x))
+TrackedNumber(x::Number) = TrackedNumber(Tracked(Call(nothing), x, zero(x)))
 
 tracker(x::TrackedNumber) = x.tracker
 
-track(f::Call, x::Number) = TrackedNumber(Tracked(f, x))
+track(f::Call, x::Number) = TrackedNumber(Tracked(f, x, zero(x)))
 
 back!(x::TrackedNumber) = back!(x, 1)