diff --git a/base/abstractarray.jl b/base/abstractarray.jl
index b710c35a0876b..3df537239768d 100644
--- a/base/abstractarray.jl
+++ b/base/abstractarray.jl
@@ -1139,10 +1139,10 @@ function copyto!(B::AbstractVecOrMat{R}, ir_dest::AbstractRange{Int}, jr_dest::A
     return B
 end
 
-function copyto_axcheck!(dest, src)
-    @noinline checkaxs(axd, axs) = axd == axs || throw(DimensionMismatch("axes must agree, got $axd and $axs"))
+@noinline _checkaxs(axd, axs) = axd == axs || throw(DimensionMismatch("axes must agree, got $axd and $axs"))
 
-    checkaxs(axes(dest), axes(src))
+function copyto_axcheck!(dest, src)
+    _checkaxs(axes(dest), axes(src))
     copyto!(dest, src)
 end
 
diff --git a/base/bitarray.jl b/base/bitarray.jl
index 73f274df44a85..c6e65a3d44f9d 100644
--- a/base/bitarray.jl
+++ b/base/bitarray.jl
@@ -501,40 +501,38 @@ function Array{T,N}(B::BitArray{N}) where {T,N}
 end
 
 BitArray(A::AbstractArray{<:Any,N}) where {N} = BitArray{N}(A)
+
 function BitArray{N}(A::AbstractArray{T,N}) where N where T
     B = BitArray(undef, convert(Dims{N}, size(A)::Dims{N}))
+    _checkaxs(axes(B), axes(A))
+    copyto!(B, A)
+    return B::BitArray{N}
+end
+
+function copyto!(B::BitArray, A::AbstractArray)
     Bc = B.chunks
     l = length(B)
     l == 0 && return B
-    ind = 1
+    Ai = first(eachindex(A))
     @inbounds begin
         for i = 1:length(Bc)-1
             c = UInt64(0)
             for j = 0:63
-                c |= (UInt64(convert(Bool, A[ind])::Bool) << j)
-                ind += 1
+                c |= (UInt64(convert(Bool, A[Ai])::Bool) << j)
+                Ai = nextind(A, Ai)
             end
             Bc[i] = c
         end
         c = UInt64(0)
         for j = 0:_mod64(l-1)
-            c |= (UInt64(convert(Bool, A[ind])::Bool) << j)
-            ind += 1
+            c |= (UInt64(convert(Bool, A[Ai])::Bool) << j)
+            Ai = nextind(A, Ai)
         end
         Bc[end] = c
     end
     return B
 end
 
-function BitArray{N}(A::Array{Bool,N}) where N
-    B = BitArray(undef, size(A))
-    Bc = B.chunks
-    l = length(B)
-    l == 0 && return B
-    copy_to_bitarray_chunks!(Bc, 1, A, 1, l)
-    return B::BitArray{N}
-end
-
 reinterpret(::Type{Bool}, B::BitArray, dims::NTuple{N,Int}) where {N} = reinterpret(B, dims)
 reinterpret(B::BitArray, dims::NTuple{N,Int}) where {N} = reshape(B, dims)
 
@@ -721,24 +719,25 @@ function _unsafe_setindex!(B::BitArray, X::AbstractArray, I::BitArray)
     lx = length(X)
     last_chunk_len = _mod64(length(B)-1)+1
 
-    c = 1
+    Xi = first(eachindex(X))
+    lastXi = last(eachindex(X))
     for i = 1:lc
         @inbounds Imsk = Ic[i]
         @inbounds C = Bc[i]
         u = UInt64(1)
         for j = 1:(i < lc ? 64 : last_chunk_len)
             if Imsk & u != 0
-                lx < c && throw_setindex_mismatch(X, c)
-                @inbounds x = convert(Bool, X[c])
+                Xi > lastXi && throw_setindex_mismatch(X, count(I))
+                @inbounds x = convert(Bool, X[Xi])
                 C = ifelse(x, C | u, C & ~u)
-                c += 1
+                Xi = nextind(X, Xi)
             end
             u <<= 1
         end
         @inbounds Bc[i] = C
     end
-    if length(X) != c-1
-        throw_setindex_mismatch(X, c-1)
+    if Xi != nextind(X, lastXi)
+        throw_setindex_mismatch(X, count(I))
     end
     return B
 end
diff --git a/test/bitarray.jl b/test/bitarray.jl
index d17a9856596a4..250e16e31d32d 100644
--- a/test/bitarray.jl
+++ b/test/bitarray.jl
@@ -1787,3 +1787,34 @@ end
         @test all(bitarray[rangein, rangeout] .== true)
     end
 end
+
+# issue #45825
+
+isdefined(Main, :OffsetArrays) || @eval Main include("testhelpers/OffsetArrays.jl")
+using .Main.OffsetArrays
+
+let all_false = OffsetArray(falses(2001), -1000:1000)
+    @test !any(==(true), all_false)
+    # should be run with --check-bounds=yes
+    @test_throws DimensionMismatch BitArray(all_false)
+    all_false = OffsetArray(falses(2001), 1:2001)
+    @test !any(==(true), BitArray(all_false))
+    all_false = OffsetArray(falses(100, 100), 0:99, -1:98)
+    @test !any(==(true), all_false)
+    @test_throws DimensionMismatch BitArray(all_false)
+    all_false = OffsetArray(falses(100, 100), 1:100, 1:100)
+    @test !any(==(true), all_false)
+end
+let a = falses(1000),
+    msk = BitArray(rand(Bool, 1000)),
+    n = count(msk),
+    b = OffsetArray(rand(Bool, n), (-n÷2):(n÷2)-iseven(n))
+    a[msk] = b
+    @test a[msk] == collect(b)
+    a = falses(100, 100)
+    msk = BitArray(rand(Bool, 100, 100))
+    n = count(msk)
+    b = OffsetArray(rand(Bool, 1, n), 1:1, (-n÷2):(n÷2)-iseven(n))
+    a[msk] = b
+    @test a[msk] == vec(collect(b))
+end