diff --git a/src/FFTViews.jl b/src/FFTViews.jl
index c53d941..83eece9 100644
--- a/src/FFTViews.jl
+++ b/src/FFTViews.jl
@@ -1,6 +1,6 @@
 module FFTViews
 
-using Base: tail, unsafe_length, @propagate_inbounds
+using Base: tail, @propagate_inbounds
 using FFTW
 
 # A custom rangetype that will be used for indices and never throws a
@@ -69,9 +69,9 @@ function Base.similar(A::AbstractArray, T::Type, shape::Tuple{FFTVRange,Vararg{F
     FFTView(similar(A, T, map(length, shape)))
 end
 
-function Base.similar(f::Union{Function,Type}, shape::Tuple{FFTVRange,Vararg{FFTVRange}})
+function Base.similar(::Type{AA}, shape::Tuple{FFTVRange,Vararg{FFTVRange}}) where AA<:AbstractArray
     all(x->first(x)==0, shape) || throw(BoundsError("cannot allocate FFTView with the first element of the range non-zero"))
-    FFTView(similar(f, map(length, shape)))
+    FFTView(similar(AA, map(length, shape)))
 end
 
 Base.reshape(F::FFTView{_,N}, ::Type{Val{N}}) where {_,N}   = F
@@ -86,6 +86,6 @@ FFTW.rfft(F::FFTView, dims; kwargs...) = rfft(parent(F), dims; kwargs...)
 reindex(::Type{V}, ::Tuple{}, ::Tuple{}) where {V} = ()
 _reindex(::Type{FFTView}, ind, i) = modrange(i+1, ind)
 
-modrange(i, rng::AbstractUnitRange) = mod(i-first(rng), unsafe_length(rng))+first(rng)
+modrange(i, rng::AbstractUnitRange) = mod(i-first(rng), length(rng))+first(rng)
 
 end # module
diff --git a/test/runtests.jl b/test/runtests.jl
index 990d081..4e0a292 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,10 +1,13 @@
 using FFTViews
 using FFTW
+using OffsetArrays
 using Test
 
+@test isempty(detect_ambiguities(FFTViews))
+
 function test_approx_eq_periodic(a::FFTView, b)
     for I in CartesianIndices(axes(b))
-        @test a[I-one(I)] ≈ b[I]
+        @test a[I-oneunit(I)] ≈ b[I]
     end
     nothing
 end
@@ -42,6 +45,8 @@ end
     @test reshape(a, Val{2}) === a
     @test reshape(a, Val{1}) == FFTView(convert(Vector{Float64}, collect(1:35)))
     @test axes(reshape(a, Val{3})) == (0:4,0:6,0:0)
+    # issue #20
+    @test FFTView(ones((3))) .+ 1 == FFTView(fill(2, 3))
 end
 
 @testset "convolution-shift" begin
@@ -78,8 +83,6 @@ end
     end
 end
 
-using OffsetArrays
-
 @testset "convolution-offset" begin
     for l2 in (8,9), l1 in (8,9)
         a = OffsetArray(zeros(l1,l2), (-2,-3))