diff --git a/src/GenericCyclotomics.jl b/src/GenericCyclotomics.jl
index 6c963ef..7293179 100644
--- a/src/GenericCyclotomics.jl
+++ b/src/GenericCyclotomics.jl
@@ -2,7 +2,7 @@ using Oscar.Random: Random, SamplerTrivial, GLOBAL_RNG
 using Oscar.RandomExtensions: RandomExtensions, Make2, AbstractRNG
 
 import Oscar.AbstractAlgebra: parent_type, elem_type, base_ring, base_ring_type, parent, is_domain_type,
-	is_exact_type, canonical_unit, isequal, divexact, zero!, mul!, add!, addeq!, get_cached!, is_unit,
+	is_exact_type, canonical_unit, isequal, divexact, zero!, mul!, add!, get_cached!, is_unit,
 	characteristic, Ring, RingElem, expressify, evaluate, normal_form, divexact
 import Oscar: pretty, Indent, Dedent, terse, is_terse
 import Base: show, +, -, *, ^, ==, inv, isone, iszero, one, zero, rand, deepcopy_internal, hash, conj, promote_rule
@@ -367,10 +367,13 @@ end
 
 mul!(x::GenericCyclo, y::GenericCyclo, z::GenericCyclo) = y*z
 
-add!(x::GenericCyclo, y::GenericCyclo, z::GenericCyclo) = y+z
-
-function addeq!(x::GenericCyclo, y::GenericCyclo)
-	mergewith!(+, x.f, y.f)
+function add!(x::GenericCyclo, y::GenericCyclo, z::GenericCyclo)
+	if x === z
+		y,z=z,y
+	elseif x !== y
+		x.f = deepcopy(y.f)
+	end
+	mergewith!(+, x.f, z.f)
 	strip_zeros!(x.f)
 	return x
 end
diff --git a/test/runtests.jl b/test/runtests.jl
index 4beeb4f..6881a10 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -60,6 +60,24 @@ test_Ring_interface(S)
 	@test isone((S(1)//S(2))*2)
 
 	@test conj(a//c) == conj(a)//conj(c)
+
+	x=deepcopy(a)
+	y=deepcopy(b)
+	ab=a+b
+	@test add!(y, a, y) == ab
+	@test y == ab
+	@test a == x
+
+	add!(a, a, a)
+	@test a == 2*x
+
+	y=deepcopy(b)
+	z=deepcopy(c)
+	cb=c+b
+	add!(a, c, b)
+	@test a == cb
+	@test b == y
+	@test c == z
 end
 
 @testset "Shifts" begin