diff --git a/src/FillArrays.jl b/src/FillArrays.jl
index 581e8252..d8db9f5d 100644
--- a/src/FillArrays.jl
+++ b/src/FillArrays.jl
@@ -33,6 +33,10 @@ const AbstractFillVecOrMat{T} = Union{AbstractFillVector{T},AbstractFillMatrix{T
 
 ==(a::AbstractFill, b::AbstractFill) = axes(a) == axes(b) && getindex_value(a) == getindex_value(b)
 
+@inline function Base.isassigned(F::AbstractFill, i::Integer...)
+    @boundscheck checkbounds(Bool, F, to_indices(F, i)...) || return false
+    return true
+end
 
 @inline function _fill_getindex(F::AbstractFill, kj::Integer...)
     @boundscheck checkbounds(F, kj...)
diff --git a/src/oneelement.jl b/src/oneelement.jl
index b731071f..f6204abb 100644
--- a/src/oneelement.jl
+++ b/src/oneelement.jl
@@ -97,6 +97,11 @@ julia> FillArrays.getindex_value(A)
 """
 getindex_value(A::OneElement) = all(in.(A.ind, axes(A))) ? A.val : zero(eltype(A))
 
+@inline function Base.isassigned(F::OneElement, i::Integer...)
+    @boundscheck checkbounds(Bool, F, to_indices(F, i)...) || return false
+    return true
+end
+
 Base.AbstractArray{T,N}(A::OneElement{<:Any,N}) where {T,N} = OneElement(T(A.val), A.ind, A.axes)
 
 Base.replace_in_print_matrix(o::OneElementVector, k::Integer, j::Integer, s::AbstractString) =
diff --git a/test/runtests.jl b/test/runtests.jl
index 2fd3c5ca..8af5ed45 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -261,6 +261,15 @@ end
     end
 end
 
+@testset "isassigned" begin
+    for f in (Fill("", 3, 4), Zeros(3,4), Ones(3,4))
+        @test !isassigned(f, 0, 0)
+        @test isassigned(f, 2, 2)
+        @test !isassigned(f, 10, 10)
+        @test_throws ArgumentError isassigned(f, true)
+    end
+end
+
 @testset "indexing" begin
     A = Fill(3.0,5)
     @test A[1:3] ≡ Fill(3.0,3)
@@ -2184,6 +2193,14 @@ end
         @test adjoint(A) == OneElement(3, (1,2), (1,4))
     end
 
+    @testset "isassigned" begin
+        f = OneElement(2, (3,3), (4,4))
+        @test !isassigned(f, 0, 0)
+        @test isassigned(f, 2, 2)
+        @test !isassigned(f, 10, 10)
+        @test_throws ArgumentError isassigned(f, true)
+    end
+
     @testset "matmul" begin
         A = reshape(Float64[1:9;], 3, 3)
         v = reshape(Float64[1:3;], 3)