diff --git a/src/states/finitemps.jl b/src/states/finitemps.jl
index 9d0fe986a..279de9b24 100644
--- a/src/states/finitemps.jl
+++ b/src/states/finitemps.jl
@@ -311,6 +311,8 @@ function Base.similar(ψ::FiniteMPS{A, B}) where {A, B}
     return FiniteMPS{A, B}(similar(ψ.ALs), similar(ψ.ARs), similar(ψ.ACs), similar(ψ.Cs))
 end
 
+Base.isfinite(ψ::FiniteMPS) = true
+
 Base.eachindex(ψ::FiniteMPS) = eachindex(ψ.AL)
 Base.eachindex(l::IndexStyle, ψ::FiniteMPS) = eachindex(l, ψ.AL)
 Base.checkbounds(::Type{Bool}, ψ::FiniteMPS, i::Integer) = 1 <= i <= length(ψ)
diff --git a/src/states/infinitemps.jl b/src/states/infinitemps.jl
index c9a4cf906..27c02dd2a 100644
--- a/src/states/infinitemps.jl
+++ b/src/states/infinitemps.jl
@@ -241,6 +241,7 @@ Base.size(ψ::InfiniteMPS, args...) = size(ψ.AL, args...)
 Base.length(ψ::InfiniteMPS) = length(ψ.AL)
 Base.eltype(ψ::InfiniteMPS) = eltype(typeof(ψ))
 Base.eltype(::Type{<:InfiniteMPS{A}}) where {A} = A
+Base.isfinite(ψ::InfiniteMPS) = false
 
 Base.copy(ψ::InfiniteMPS) = InfiniteMPS(copy(ψ.AL), copy(ψ.AR), copy(ψ.C), copy(ψ.AC))
 function Base.copy!(ψ::InfiniteMPS, ϕ::InfiniteMPS)
diff --git a/src/states/multilinemps.jl b/src/states/multilinemps.jl
index 6f1199095..73f68fac6 100644
--- a/src/states/multilinemps.jl
+++ b/src/states/multilinemps.jl
@@ -13,7 +13,7 @@ Type that represents multiple lines of `InfiniteMPS` objects.
                  virtualspaces::Matrix{<:Union{S, CompositeSpace{S}}) where
                  {S<:ElementarySpace}
     MultilineMPS(As::AbstractMatrix{<:GenericMPSTensor}; kwargs...)
-    MultilineMPS(ALs::AbstractMatrix{<:GenericMPSTensor}, 
+    MultilineMPS(ALs::AbstractMatrix{<:GenericMPSTensor},
                  C₀::AbstractVector{<:MPSBondTensor}; kwargs...)
 
 See also: [`Multiline`](@ref)
@@ -101,6 +101,8 @@ Base.convert(::Type{InfiniteMPS}, st::MultilineMPS) = only(st)
 Base.eltype(t::MultilineMPS) = eltype(t[1])
 Base.copy!(ψ::MultilineMPS, ϕ::MultilineMPS) = (copy!.(parent(ψ), parent(ϕ)); ψ)
 
+Base.isfinite(ψ::MultilineMPS) = false
+
 for f_space in (:physicalspace, :left_virtualspace, :right_virtualspace)
     @eval $f_space(t::MultilineMPS, i::Int, j::Int) = $f_space(t[i], j)
     @eval $f_space(t::MultilineMPS, I::CartesianIndex{2}) = $f_space(t, Tuple(I)...)
diff --git a/test/states.jl b/test/states.jl
index 04990ea50..7762b844c 100644
--- a/test/states.jl
+++ b/test/states.jl
@@ -24,6 +24,7 @@ module TestStates
         L = rand(3:20)
         ψ = FiniteMPS(rand, elt, L, d, D)
 
+        @test isfinite(ψ)
         @test @constinferred physicalspace(ψ) == fill(d, L)
         @test all(x -> x ≾ D, @constinferred left_virtualspace(ψ))
         @test all(x -> x ≾ D, @constinferred right_virtualspace(ψ))
@@ -99,6 +100,7 @@ module TestStates
 
         ψ = InfiniteMPS([rand(elt, D * d, D), rand(elt, D * d, D)]; tol)
 
+        @test !isfinite(ψ)
         @test physicalspace(ψ) == fill(d, 2)
         @test all(x -> x ≾ D, left_virtualspace(ψ))
         @test all(x -> x ≾ D, right_virtualspace(ψ))