diff --git a/test/abi.jl b/test/abi.jl
index 7a7917553f..5acb30e04f 100644
--- a/test/abi.jl
+++ b/test/abi.jl
@@ -480,19 +480,6 @@ mulsin(x) = sin(x[1] * x[2])
     @test Enzyme.autodiff(ForwardWithPrimal, () -> Enzyme.within_autodiff())[1]
 end
 
-mutable struct ConstVal
-    x::Float64
-    const y::Float64
-end
-
-@testset "Make Zero" begin
-    v = ConstVal(2.0, 3.0)
-    dv = make_zero(v)
-    @test dv isa ConstVal
-    @test dv.x ≈ 0.0
-    @test dv.y ≈ 0.0
-end
-
 @testset "Type inference" begin
     x = ones(10)
     @inferred autodiff(Enzyme.Reverse, abssum, Duplicated(x,x))
diff --git a/test/make_zero.jl b/test/make_zero.jl
new file mode 100644
index 0000000000..ee88ad1498
--- /dev/null
+++ b/test/make_zero.jl
@@ -0,0 +1,322 @@
+using Enzyme
+using Test
+
+mutable struct MutableWrapper{T}
+    x::T
+end
+
+Base.:(==)(a::MutableWrapper, b::MutableWrapper) = (a === b) || isequal(a.x, b.x)
+
+struct Incomplete{T}
+    s::String
+    x::Float64
+    w::T
+    z  # not initialized
+    Incomplete(s, x, w) = new{typeof(w)}(s, x, w)
+end
+
+function Base.:(==)(a::Incomplete, b::Incomplete)
+    (a === b) && return true
+    (isequal(a.s, b.s) && isequal(a.x, b.x) && isequal(a.w, b.w)) || return false
+    if isdefined(a, :z) && isdefined(b, :z)
+        isequal(a.z, b.z) || return false
+    elseif isdefined(a, :z) || isdefined(b, :z)
+        return false
+    end
+    return true
+end
+
+mutable struct MutableIncomplete{T}
+    s::String
+    const x::Float64
+    y::Float64
+    z  # not initialized
+    w::T
+    function MutableIncomplete(s, x, y, w)
+        ret = new{typeof(w)}(s, x, y)
+        ret.w = w
+        return ret
+    end
+end
+
+function Base.:(==)(a::MutableIncomplete, b::MutableIncomplete)
+    (a === b) && return true
+    if !isequal(a.s, b.s) || !isequal(a.x, b.x) || !isequal(a.y, b.y) || !isequal(a.w, b.w)
+        return false
+    end
+    if isdefined(a, :z) && isdefined(b, :z)
+        isequal(a.z, b.z) || return false
+    elseif isdefined(a, :z) || isdefined(b, :z)
+        return false
+    end
+    return true
+end
+
+@testset "make_zero" begin
+    # floats
+    @test make_zero(1.0) == 0.0
+    @test make_zero(1.0im) == 0.0im
+
+    # float arrays + multiple references
+    rearr = [1.0]
+    imarr = [1.0im]
+    rearr0 = make_zero(rearr)
+    imarr0 = make_zero(imarr)
+    @test typeof(rearr0) === typeof(rearr)
+    @test typeof(imarr0) === typeof(imarr)
+    @test rearr == [1.0]    # no mutation
+    @test imarr == [1.0im]  # no mutation
+    @test rearr0 == [0.0]
+    @test imarr0 == [0.0im]
+    rearrs0 = make_zero((rearr, rearr))
+    imarrs0 = make_zero((imarr, imarr))
+    @test typeof(rearrs0) === typeof((rearr, rearr))
+    @test typeof(imarrs0) === typeof((imarr, imarr))
+    @test rearr == [1.0]    # no mutation
+    @test imarr == [1.0im]  # no mutation
+    @test rearrs0[1] === rearrs0[2]
+    @test imarrs0[1] === imarrs0[2]
+    @test rearrs0[1] == [0.0]
+    @test imarrs0[1] == [0.0im]
+
+    # floats in structs
+    rewrapped = MutableWrapper(1.0)
+    imwrapped = MutableWrapper(1.0im)
+    rewrapped0 = make_zero(rewrapped)
+    imwrapped0 = make_zero(imwrapped)
+    @test typeof(rewrapped0) === typeof(rewrapped)
+    @test typeof(imwrapped0) === typeof(imwrapped)
+    @test rewrapped == MutableWrapper(1.0)    # no mutation
+    @test imwrapped == MutableWrapper(1.0im)  # no mutation
+    @test rewrapped0 == MutableWrapper(0.0)
+    @test imwrapped0 == MutableWrapper(0.0im)
+
+    # generic array + multiple references
+    wrapped = MutableWrapper(1.0)
+    mixarr = ["a", 1.0, wrapped]
+    mixarr0 = make_zero(mixarr)
+    @test typeof(mixarr0) === typeof(mixarr)
+    @test view(mixarr, 1:2) == ["a", 1.0]  # no mutation
+    @test mixarr[3] === wrapped            # no mutation
+    @test mixarr0 == ["a", 0.0, MutableWrapper(0.0)]
+    mixarrs0 = make_zero((mixarr, mixarr))
+    @test typeof(mixarrs0) === typeof((mixarr, mixarr))
+    @test view(mixarr, 1:2) == ["a", 1.0]  # no mutation
+    @test mixarr[3] === wrapped            # no mutation
+    @test mixarrs0[1] === mixarrs0[2]
+    @test mixarrs0[1] == ["a", 0.0, MutableWrapper(0.0)]
+
+    # non-differentiable array + copy_if_inactive
+    constarr = ["a"]
+    constarr0 = make_zero(constarr)
+    @test typeof(constarr0) === typeof(constarr)
+    @test constarr == ["a"]  # no mutation
+    @test constarr0 === constarr
+    constarr0copy = make_zero(constarr, #=copy_if_inactive=#Val(true))
+    @test typeof(constarr0copy) === typeof(constarr0)
+    @test constarr == ["a"]  # no mutation
+    @test constarr0copy !== constarr
+    @test constarr0copy == constarr
+
+    # Tuple
+    tup = ("a", 1.0, MutableWrapper(1.0))
+    tup0 = make_zero(tup)
+    @test typeof(tup0) === typeof(tup)
+    @test tup == ("a", 1.0, MutableWrapper(1.0))  # no mutation
+    @test tup0 == ("a", 0.0, MutableWrapper(0.0))
+
+    # NamedTuple
+    ntup = (a="a", b=1.0, c=MutableWrapper(1.0))
+    ntup0 = make_zero(ntup)
+    @test typeof(ntup0) === typeof(ntup)
+    @test ntup == (a="a", b=1.0, c=MutableWrapper(1.0))  # no mutation
+    @test ntup0 == (a="a", b=0.0, c=MutableWrapper(0.0))
+
+    # Box + multiple references
+    box = Core.Box(1.0)
+    box0 = make_zero(box)
+    @test typeof(box0) === typeof(box)
+    @test box.contents == 1.0  # no mutation
+    @test box0.contents == 0.0
+    boxes0 = make_zero((box, box))
+    @test typeof(boxes0) === typeof((box, box))
+    @test box.contents == 1.0  # no mutation
+    @test boxes0[1] === boxes0[2]
+    @test boxes0[1].contents == 0.0
+
+    # differentiable custom type + multiple references
+    wrapped = MutableWrapper(1.0)
+    wrapped0 = make_zero(wrapped)
+    @test typeof(wrapped0) === typeof(wrapped)
+    @test wrapped == MutableWrapper(1.0)  # no mutation
+    @test wrapped0 == MutableWrapper(0.0)
+    wrappeds0 = make_zero((wrapped, wrapped))
+    @test typeof(wrappeds0) === typeof((wrapped, wrapped))
+    @test wrapped == MutableWrapper(1.0)  # no mutation
+    @test wrappeds0[1] === wrappeds0[2]
+    @test wrappeds0[1] == MutableWrapper(0.0)
+
+    # non-differentiable custom type + copy_if_inactive
+    constwrapped = MutableWrapper("a")
+    constwrapped0 = make_zero(constwrapped)
+    @test typeof(constwrapped0) === typeof(constwrapped)
+    @test constwrapped == MutableWrapper("a")  # no mutation
+    @test constwrapped0 === constwrapped
+    constwrapped0copy = make_zero(constwrapped, #=copy_if_inactive=#Val(true))
+    @test typeof(constwrapped0copy) === typeof(constwrapped0)
+    @test constwrapped == MutableWrapper("a")  # no mutation
+    @test constwrapped0copy !== constwrapped
+    @test constwrapped0copy == constwrapped
+
+    # immutable struct with active, mutable, inactive and undefined fields
+    incomplete = Incomplete("a", 1.0, MutableWrapper(1.0))
+    incomplete0 = make_zero(incomplete)
+    @test typeof(incomplete0) === typeof(incomplete)
+    @test incomplete == Incomplete("a", 1.0, MutableWrapper(1.0))  # no mutation
+    @test incomplete0 == Incomplete("a", 0.0, MutableWrapper(0.0))
+
+    # mutable struct with inactive, active, undefined, and mutable fields
+    # + multiple references
+    incompletemut = MutableIncomplete("a", 1.0, 1.0, MutableWrapper(1.0))
+    incompletemut0 = make_zero(incompletemut)
+    @test typeof(incompletemut0) === typeof(incompletemut)
+    @test incompletemut == MutableIncomplete("a", 1.0, 1.0, MutableWrapper(1.0))  # no mutation
+    @test incompletemut0 == MutableIncomplete("a", 0.0, 0.0, MutableWrapper(0.0))
+    incompletemuts0 = make_zero((incompletemut, incompletemut))
+    @test typeof(incompletemuts0) === typeof((incompletemut, incompletemut))
+    @test incompletemut == MutableIncomplete("a", 1.0, 1.0, MutableWrapper(1.0))  # no mutation
+    @test incompletemuts0[1] === incompletemuts0[2]
+    @test incompletemuts0[1] == MutableIncomplete("a", 0.0, 0.0, MutableWrapper(0.0))
+end
+
+@testset "make_zero!" begin
+    # floats in mutable struct
+    rewrapped, imwrapped = MutableWrapper(1.0), MutableWrapper(1.0im)
+    make_zero!(rewrapped)
+    make_zero!(imwrapped)
+    @test rewrapped == MutableWrapper(0.0)
+    @test imwrapped == MutableWrapper(0.0im)
+
+    # mixed tuple in mutable container
+    wrapped = MutableWrapper(1.0)
+    tuparr = [(1.0, wrapped)]
+    make_zero!(tuparr)
+    @test tuparr[1] === (0.0, wrapped)
+    @test wrapped == MutableWrapper(0.0)
+
+    # mixed namedtuple in mutable container
+    wrapped = MutableWrapper(1.0)
+    ntuparr = [(a=1.0, b=wrapped)]
+    make_zero!(ntuparr)
+    @test ntuparr[1] === (a=0.0, b=wrapped)
+    @test wrapped == MutableWrapper(0.0)
+
+    # immutable struct with active, mutable, inactive and undefined fields in mutable container
+    wrapped = MutableWrapper(1.0)
+    incompletearr = [Incomplete("a", 1.0, wrapped)]
+    make_zero!(incompletearr)
+    @test incompletearr[1] == Incomplete("a", 0.0, wrapped)
+    @test wrapped == MutableWrapper(0.0)
+
+    # floats in Ref
+    reref, imref = Ref(1.0), Ref(1.0im)
+    make_zero!(reref)
+    make_zero!(imref)
+    @test reref[] == 0.0
+    @test imref[] == 0.0im
+
+    # float arrays
+    rearr, imarr = [1.0], [1.0im]
+    make_zero!(rearr)
+    make_zero!(imarr)
+    @test rearr[1] == 0.0
+    @test imarr[1] == 0.0im
+
+    # non-differentiable array
+    constarr = ["a"]
+    make_zero!(constarr)
+    @test constarr[1] == "a"
+
+    # array with active, mutable, inactive and unassigned elements + multiple references
+    wrapped = MutableWrapper(1.0)
+    genericarr = Vector(undef, 4)
+    genericarr[1:3] .= ("a", 1.0, wrapped)
+    genericarrs = [genericarr, genericarr]
+    make_zero!(genericarrs)
+    @test genericarrs[1] === genericarrs[2]
+    @test genericarrs[1] === genericarr
+    @test view(genericarr, 1:2) == ["a", 0.0]
+    @test genericarr[3] === wrapped
+    @test wrapped == MutableWrapper(0.0)
+    @test !isassigned(genericarr, 4)
+
+    # Ref with multiple references
+    genericref = Ref((1.0,))
+    genericrefs = [genericref, genericref]
+    make_zero!(genericrefs)
+    @test genericrefs[1] === genericrefs[2]
+    @test genericrefs[1] === genericref
+    @test genericref[] == (0.0,)
+
+    # Ref with mutable value
+    wrapped = MutableWrapper(1.0)
+    mutref = Ref(wrapped)
+    make_zero!(mutref)
+    @test mutref[] === wrapped
+    @test wrapped == MutableWrapper(0.0)
+
+    # Ref with non-differentiable value
+    constref = Ref("a")
+    make_zero!(constref)
+    @test constref[] == "a"
+
+    # Box with multiple references
+    box = Core.Box(1.0)
+    boxes = [box, box]
+    make_zero!(boxes)
+    @test boxes[1] === boxes[2]
+    @test boxes[1] === box
+    @test box.contents == 0.0
+
+    # Box with mutable value
+    wrapped = MutableWrapper(1.0)
+    mutbox = Core.Box(wrapped)
+    make_zero!(mutbox)
+    @test mutbox.contents === wrapped
+    @test wrapped == MutableWrapper(0.0)
+
+    # Box with non-differentiable value
+    constbox = Core.Box("a")
+    make_zero!(constbox)
+    @test constbox.contents == "a"
+
+    # mutable struct with inactive, active, const active, undefined, and mutable fields
+    # + multiple references
+    wrapped = MutableWrapper(1.0)
+    incompletemut = MutableIncomplete("a", #=const=#1.0, 1.0, wrapped)
+    incompletemuts = [incompletemut, incompletemut]
+    make_zero!(incompletemuts)
+    @test incompletemuts[1] === incompletemuts[2]
+    @test incompletemuts[1] === incompletemut
+    @test incompletemut == MutableIncomplete("a", #=const=#0.0, 0.0, MutableWrapper(0.0))
+    @test incompletemut.w === wrapped
+
+    # wrapped differentiable array
+    arr = [1.0]
+    arrwrapped = MutableWrapper(arr)
+    make_zero!(arrwrapped)
+    @test arrwrapped.x === arr
+    @test arr == [0.0]
+
+    # early error on active/mixed type
+    @test_throws ErrorException make_zero!(1.0)
+    @test_throws ErrorException make_zero!((1.0, MutableWrapper(1.0)))
+
+    # immutable struct with both active and undefined fields in immutable container
+    # (currently fails due to #1935)
+    wrapped = MutableWrapper(1.0)
+    incompletetuparr = [(Incomplete("a", 1.0, wrapped),)]
+    make_zero!(incompletetuparr)
+    @test incompletetuparr[1][1] == Incomplete("a", 0.0, MutableWrapper(0.0))
+    @test incompletetuparr[1][1].w === wrapped
+end
diff --git a/test/runtests.jl b/test/runtests.jl
index c3856aabf1..926df097bd 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -75,6 +75,7 @@ end
 
 include("abi.jl")
 include("typetree.jl")
+include("make_zero.jl")
 
 include("rules.jl")
 include("rrules.jl")