diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ba39cc5
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+Manifest.toml
diff --git a/Manifest.toml b/Manifest.toml
deleted file mode 100644
index 1b63510..0000000
--- a/Manifest.toml
+++ /dev/null
@@ -1,21 +0,0 @@
-# This file is machine-generated - editing it directly is not advised
-
-[[Base64]]
-uuid = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"
-
-[[MacroTools]]
-deps = ["Markdown", "Random"]
-git-tree-sha1 = "5a5bc6bf062f0f95e62d0fe0a2d99699fed82dd9"
-uuid = "1914dd2f-81c6-5fcd-8719-6d5c9610ff09"
-version = "0.5.8"
-
-[[Markdown]]
-deps = ["Base64"]
-uuid = "d6f4376e-aef5-505a-96c1-9c027394607a"
-
-[[Random]]
-deps = ["Serialization"]
-uuid = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
-
-[[Serialization]]
-uuid = "9e88b42a-f829-5b0c-bbe9-9e923198166b"
diff --git a/Project.toml b/Project.toml
index 91dda09..8d967ff 100644
--- a/Project.toml
+++ b/Project.toml
@@ -3,6 +3,7 @@ uuid = "700de1a5-db45-46bc-99cf-38207098b444"
 version = "0.2.2"
 
 [deps]
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 MacroTools = "1914dd2f-81c6-5fcd-8719-6d5c9610ff09"
 
 [compat]
diff --git a/src/adjoint.jl b/src/adjoint.jl
index 47f628e..6255fe5 100644
--- a/src/adjoint.jl
+++ b/src/adjoint.jl
@@ -1,5 +1,6 @@
 using MacroTools
 using MacroTools: @q, combinedef
+using ChainRulesCore: AbstractZero
 
 function named(arg)
   if isexpr(arg, :(::)) && length(arg.args) == 1
@@ -63,13 +64,19 @@ function gradm(ex, mut = false, keepthunks = false)
     $adj
     @inline function ZygoteRules._pullback($cx, $f::$T, $(args...)) where $(Ts...)
       y, _back = adjoint(__context__, $f, $(argnames...))
-      $(mut ? nothing : :(back(::Nothing) = nothing))
+      $(mut ? nothing : quote
+        back(::Nothing) = nothing
+        back(Δ::AbstractZero) = $gradtuple(ntuple(_ -> Δ, $(length(args))))
+      end)
       back(Δ) = $gradtuple(_back($maybe_unthunked_Δ))
       return y, back
     end
     @inline function ZygoteRules._pullback($cx, ::$kT, kw, $f::$T, $(args...)) where $(Ts...)
       y, _back = adjoint(__context__, $f, $(argnames...); kw...)
-      $(mut ? nothing : :(back(::Nothing) = nothing))
+      $(mut ? nothing : quote
+        back(::Nothing) = nothing
+        back(Δ::AbstractZero) = $gradtuplekw(ntuple(_ -> Δ, $(length(args))))
+      end)
       back(Δ) = $gradtuplekw(_back($maybe_unthunked_Δ))
       return y, back
     end