diff --git a/src/compiler.jl b/src/compiler.jl
index 83ff363dbd..57086a2ec6 100644
--- a/src/compiler.jl
+++ b/src/compiler.jl
@@ -1335,7 +1335,7 @@ end
 function make_zero_immutable!(prev::T, seen::S)::T where {T <: Tuple, S}
     ntuple(Val(length(T.parameters))) do i
         Base.@_inline_meta
-        make_zero_immutable(prev[i], seen)
+        make_zero_immutable!(prev[i], seen)
     end
 end
 
@@ -1343,7 +1343,7 @@ function make_zero_immutable!(prev::NamedTuple{a, b}, seen::S)::NamedTuple{a, b}
     NamedTuple{a, b}(
     ntuple(Val(length(T.parameters))) do i
         Base.@_inline_meta
-        make_zero_immutable(prev[a[i]], seen)
+        make_zero_immutable!(prev[a[i]], seen)
     end
     )
 end
@@ -1353,7 +1353,7 @@ function make_zero_immutable!(prev::T, seen::S)::T where {T, S}
     if guaranteed_const_nongen(T, nothing)
         return prev
     end
-    @assert !mutable_register(T)
+    @assert !ismutable(T)
 
     @assert !Base.isabstracttype(RT)
     @assert Base.isconcretetype(RT)
@@ -1364,11 +1364,11 @@ function make_zero_immutable!(prev::T, seen::S)::T where {T, S}
         if isdefined(prev, i)
             xi = getfield(prev, i)
             ST = Core.Typeof(xi)
-            flds[i] = if mutable_register(ST)
+            flds[i] = if active_reg_inner(ST, (), nothing, #=justActive=#Val(true)) == ActiveState
+                make_zero_immutable!(xi, seen)
+            else
                 EnzymeCore.make_zero!(xi, seen)
                 xi
-            else
-                make_zero_immutable!(xi, seen)
             end
         else
             nf = i - 1 # rest of tail must be undefined values
@@ -1422,20 +1422,20 @@ end
     if guaranteed_const_nongen(T, nothing)
         return
     end
-    if haskey(seen, prev)
+    if in(seen, prev)
         return
     end
-    insert!(seen, prev)
+    push!(seen, prev)
 
     for I in eachindex(prev)
         if isassigned(prev, I)
             pv = prev[I]
             SBT = Core.Typeof(pv)
-            if mutable_register(SBT)
-                EnzymeCore.make_zero!(pv, seen)
+            if active_reg_inner(SBT, (), nothing, #=justActive=#Val(true)) == ActiveState
+                @inbounds prev[I] = EnzymeCore.make_zero_immutable!(pv, seen)
                 nothing
             else
-                @inbounds prev[I] = EnzymeCore.make_zero_immutable!(pv, seen)
+                EnzymeCore.make_zero!(pv, seen)
                 nothing
             end
         end
@@ -1447,18 +1447,18 @@ end
     if guaranteed_const_nongen(T, nothing)
         return
     end
-    if haskey(seen, prev)
+    if in(seen, prev)
         return
     end
-    insert!(seen, prev)
+    push!(seen, prev)
 
     pv = prev[]
     SBT = Core.Typeof(pv)
-    if mutable_register(SBT)
-        EnzymeCore.make_zero!(pv, seen)
+    if active_reg_inner(SBT, (), nothing, #=justActive=#Val(true)) == ActiveState
+        prev[] = EnzymeCore.make_zero_immutable!(pv, seen)
         nothing
     else
-        prev[] = EnzymeCore.make_zero_immutable!(pv, seen)
+        EnzymeCore.make_zero!(pv, seen)
         nothing
     end
     nothing
@@ -1470,48 +1470,51 @@ end
     if guaranteed_const_nongen(T, nothing)
         return
     end
-    if haskey(seen, prev)
+    if in(seen, prev)
         return
     end
-    insert!(seen, prev)
+    push!(seen, prev)
     SBT = Core.Typeof(pv)
-    if mutable_register(SBT)
-        EnzymeCore.make_zero!(pv, seen)
+    if active_reg_inner(SBT, (), nothing, #=justActive=#Val(true)) == ActiveState
+        prev.contents = EnzymeCore.make_zero_immutable!(pv, seen)
         nothing
     else
-        prev.contents = EnzymeCore.make_zero_immutable!(pv, seen)
+        EnzymeCore.make_zero!(pv, seen)
         nothing
     end
     nothing
 end
 
-@inline function EnzymeCore.make_zero!(prev::T, seen::S=IdSet{Any}())::Nothing where {T, S}
+@inline function EnzymeCore.make_zero!(prev::T, seen::S=Base.IdSet{Any}())::Nothing where {T, S}
     if guaranteed_const_nongen(T, nothing)
         return
     end
-    if haskey(seen, prev)
+    if in(seen, prev)
         return
     end
-    @assert !Base.isabstracttype(RT)
-    @assert Base.isconcretetype(RT)
-    nf = fieldcount(RT)
+    @assert !Base.isabstracttype(T)
+    @assert Base.isconcretetype(T)
+    nf = fieldcount(T)
     
 
     if nf == 0
         return
     end
 
-    insert!(seen, prev)
+    push!(seen, prev)
 
     for i in 1:nf
         if isdefined(prev, i)
             xi = getfield(prev, i)
-            SBT = Core.Typeof(pv)
-            if mutable_register(SBT)
-                EnzymeCore.make_zero!(xi, seen)
+            SBT = Core.Typeof(xi)
+            if guaranteed_const_nongen(SBT, nothing)
+                continue
+            end
+            if active_reg_inner(SBT, (), nothing, #=justActive=#Val(true)) == ActiveState
+                setfield!(prev, i, make_zero_immutable!(xi, seen))
                 nothing
             else
-                setfield!(prev, i, make_zero_immutable!(xi, seen))
+                EnzymeCore.make_zero!(xi, seen)
                 nothing
             end
         end
diff --git a/test/runtests.jl b/test/runtests.jl
index 225ddf435f..0212ec0d83 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -181,6 +181,28 @@ end
     # @test thunk_split.primal !== C_NULL
     # @test thunk_split.primal !== thunk_split.adjoint
     # @test thunk_a.adjoint !== thunk_split.adjoint
+    #
+    z = ([3.14, 21.5, 16.7], [0,1], [5.6, 8.9])
+    Enzyme.make_zero!(z)
+    @test z[1] ≈ [0.0, 0.0, 0.0]
+    @test z[2][1] == 0
+    @test z[2][2] == 1
+    @test z[3] ≈ [0.0, 0.0]
+    
+    z2 = ([3.14, 21.5, 16.7], [0,1], [5.6, 8.9])
+    Enzyme.make_zero!(z2)
+    @test z2[1] ≈ [0.0, 0.0, 0.0]
+    @test z2[2][1] == 0
+    @test z2[2][2] == 1
+    @test z2[3] ≈ [0.0, 0.0]
+    
+    z3 = [3.4, "foo"]
+    Enzyme.make_zero!(z3)
+    @test z3[1] ≈ 0.0
+    @test z3[2] == "foo"
+
+    z4 = sin
+    Enzyme.make_zero!(z4)
 end
 
 @testset "Reflection" begin