diff --git a/Project.toml b/Project.toml
index de834436..9feabc65 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "FastTransforms"
 uuid = "057dd010-8810-581a-b7be-e3fc3b93f78c"
-version = "0.15.4"
+version = "0.15.5"
 
 [deps]
 AbstractFFTs = "621f4979-c628-5d54-868e-fcf4e3e8185c"
@@ -18,7 +18,7 @@ ToeplitzMatrices = "c751599d-da0a-543b-9d20-d0a503d91d24"
 
 [compat]
 AbstractFFTs = "1.0"
-FFTW = "~1.6"
+FFTW = "1.7"
 FastGaussQuadrature = "0.4, 0.5"
 FastTransforms_jll = "0.6.2"
 FillArrays = "0.9, 0.10, 0.11, 0.12, 0.13, 1"
diff --git a/src/chebyshevtransform.jl b/src/chebyshevtransform.jl
index c77941d8..11e07010 100644
--- a/src/chebyshevtransform.jl
+++ b/src/chebyshevtransform.jl
@@ -19,11 +19,9 @@ ChebyshevTransformPlan{T,kind}(plan::FFTW.r2rFFTWPlan{T,K,inplace,N,R}) where {T
     ChebyshevTransformPlan{T,kind,K,inplace,N,R}(plan)
 
 # jump through some hoops to make inferrable
-@inline kindtuple(N) = NTuple{N,Int32}
-@inline kindtuple(N,region...) = Vector{Int32}
 function plan_chebyshevtransform!(x::AbstractArray{T,N}, ::Val{1}, dims...; kws...) where {T<:fftwNumber,N}
     if isempty(x)
-        ChebyshevTransformPlan{T,1,kindtuple(N,dims...),true,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
+        ChebyshevTransformPlan{T,1,Vector{Int32},true,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
     else
         ChebyshevTransformPlan{T,1}(FFTW.plan_r2r!(x, FIRSTKIND, dims...; kws...))
     end
@@ -36,7 +34,7 @@ end
 
 function plan_chebyshevtransform(x::AbstractArray{T,N}, ::Val{1}, dims...; kws...) where {T<:fftwNumber,N}
     if isempty(x)
-        ChebyshevTransformPlan{T,1,kindtuple(N,dims...),false,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
+        ChebyshevTransformPlan{T,1,Vector{Int32},false,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
     else
         ChebyshevTransformPlan{T,1}(FFTW.plan_r2r(x, FIRSTKIND, dims...; kws...))
     end
@@ -250,7 +248,7 @@ inv(P::IChebyshevTransformPlan{T,1}) where {T} = ChebyshevTransformPlan{T,1}(inv
 
 function plan_ichebyshevtransform!(x::AbstractArray{T,N}, ::Val{1}, dims...; kws...) where {T<:fftwNumber,N}
     if isempty(x)
-        IChebyshevTransformPlan{T,1,kindtuple(N,dims...),true,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
+        IChebyshevTransformPlan{T,1,Vector{Int32},true,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
     else
         IChebyshevTransformPlan{T,1}(FFTW.plan_r2r!(x, IFIRSTKIND, dims...; kws...))
     end
@@ -262,7 +260,7 @@ end
 
 function plan_ichebyshevtransform(x::AbstractArray{T,N}, ::Val{1}, dims...; kws...) where {T<:fftwNumber,N}
     if isempty(x)
-        IChebyshevTransformPlan{T,1,kindtuple(N,dims...),false,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
+        IChebyshevTransformPlan{T,1,Vector{Int32},false,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
     else
         IChebyshevTransformPlan{T,1}(FFTW.plan_r2r(x, IFIRSTKIND, dims...; kws...))
     end
@@ -390,7 +388,7 @@ ChebyshevUTransformPlan{T,kind}(plan::FFTW.r2rFFTWPlan{T,K,inplace,N,R}) where {
 
 function plan_chebyshevutransform!(x::AbstractArray{T,N}, ::Val{1}, dims...; kws...) where {T<:fftwNumber,N}
     if isempty(x)
-        ChebyshevUTransformPlan{T,1,kindtuple(N,dims...),true,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
+        ChebyshevUTransformPlan{T,1,Vector{Int32},true,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
     else
         ChebyshevUTransformPlan{T,1}(FFTW.plan_r2r!(x, UFIRSTKIND, dims...; kws...))
     end
@@ -402,7 +400,7 @@ end
 
 function plan_chebyshevutransform(x::AbstractArray{T,N}, ::Val{1}, dims...; kws...) where {T<:fftwNumber,N}
     if isempty(x)
-        ChebyshevUTransformPlan{T,1,kindtuple(N,dims...),false,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
+        ChebyshevUTransformPlan{T,1,Vector{Int32},false,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
     else
         ChebyshevUTransformPlan{T,1}(FFTW.plan_r2r(x, UFIRSTKIND, dims...; kws...))
     end
@@ -511,7 +509,7 @@ IChebyshevUTransformPlan{T,kind}(F::FFTW.r2rFFTWPlan{T,K,inplace,N,R}) where {T,
 
 function plan_ichebyshevutransform!(x::AbstractArray{T,N}, ::Val{1}, dims...; kws...) where {T<:fftwNumber,N}
     if isempty(x)
-        IChebyshevUTransformPlan{T,1,kindtuple(N,dims...),true,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
+        IChebyshevUTransformPlan{T,1,Vector{Int32},true,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
     else
         IChebyshevUTransformPlan{T,1}(FFTW.plan_r2r!(x, IUFIRSTKIND, dims...; kws...))
     end
@@ -523,7 +521,7 @@ end
 
 function plan_ichebyshevutransform(x::AbstractArray{T,N}, ::Val{1}, dims...; kws...) where {T<:fftwNumber,N}
     if isempty(x)
-        IChebyshevUTransformPlan{T,1,kindtuple(N,dims...),false,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
+        IChebyshevUTransformPlan{T,1,Vector{Int32},false,N,isempty(dims) ? NTuple{N,Int} : typeof(dims[1])}()
     else
         IChebyshevUTransformPlan{T,1}(FFTW.plan_r2r(x, IUFIRSTKIND, dims...; kws...))
     end
diff --git a/test/chebyshevtests.jl b/test/chebyshevtests.jl
index ae438ac0..696c13f0 100644
--- a/test/chebyshevtests.jl
+++ b/test/chebyshevtests.jl
@@ -69,10 +69,17 @@ using FastTransforms, Test
             @test g ≈ fcopy
             @test_throws ArgumentError Pi * T[1,2]
 
-            @test chebyshevtransform(T[1]) == T[1]
-            @test ichebyshevtransform(T[1]) == T[1]
-            @test chebyshevtransform(T[]) == T[]
-            @test ichebyshevtransform(T[]) == T[]
+            v = T[1]
+            @test chebyshevtransform(v) == v
+            @test ichebyshevtransform(v) == v
+            @test chebyshevtransform!(v) === v
+            @test ichebyshevtransform!(v) === v
+
+            v = T[]
+            @test chebyshevtransform(v) == v
+            @test ichebyshevtransform(v) == v
+            @test chebyshevtransform!(v) === v
+            @test ichebyshevtransform!(v) === v
         end
     end
     @testset "Chebyshev second kind points <-> first kind coefficients" begin
@@ -192,10 +199,17 @@ using FastTransforms, Test
             @test g ≈ fcopy
             @test_throws ArgumentError Pi * T[1,2]
 
-            @test chebyshevutransform(T[1]) == T[1]
-            @test ichebyshevutransform(T[1]) == T[1]
-            @test chebyshevutransform(T[]) == T[]
-            @test ichebyshevutransform(T[]) == T[]
+            v = T[1]
+            @test chebyshevutransform(v) == v
+            @test ichebyshevutransform(v) == v
+            @test chebyshevutransform!(v) === v
+            @test ichebyshevutransform!(v) === v
+
+            v = T[]
+            @test chebyshevutransform(v) == v
+            @test ichebyshevutransform(v) == v
+            @test chebyshevutransform!(v) === v
+            @test ichebyshevutransform!(v) === v
         end
     end
     @testset "Chebyshev second kind points <-> second kind coefficients" begin