diff --git a/base/broadcast.jl b/base/broadcast.jl
index b4d89e9a5fb1b..bc1a6254e59b8 100644
--- a/base/broadcast.jl
+++ b/base/broadcast.jl
@@ -1183,7 +1183,7 @@ Base.@propagate_inbounds dotview(B::BitArray, i::BitArray) = BitMaskedBitArray(B
 Base.show(io::IO, B::BitMaskedBitArray) = foreach(arg->show(io, arg), (typeof(B), (B.parent, B.mask)))
 # Override materialize! to prevent the BitMaskedBitArray from escaping to an overrideable method
 @inline materialize!(B::BitMaskedBitArray, bc::Broadcasted{<:Any,<:Any,typeof(identity),Tuple{Bool}}) = fill!(B, bc.args[1])
-@inline materialize!(B::BitMaskedBitArray, bc::Broadcasted{<:Any}) = materialize!(SubArray(B.parent, to_indices(B.parent, (B.mask,))), bc)
+@inline materialize!(B::BitMaskedBitArray, bc::Broadcasted{<:Any}) = materialize!(@inbounds(view(B.parent, B.mask)), bc)
 function Base.fill!(B::BitMaskedBitArray, b::Bool)
     Bc = B.parent.chunks
     Ic = B.mask.chunks
diff --git a/test/broadcast.jl b/test/broadcast.jl
index 0cfede78afadf..4a01215206937 100644
--- a/test/broadcast.jl
+++ b/test/broadcast.jl
@@ -993,3 +993,11 @@ end
 
     @test Cyclotomic() .* [2, 3] == [[1, 2], [1, 2]]
 end
+
+@testset "issue #45903, in place broadcast into a bit-masked bitmatrix" begin
+    A = BitArray(ones(3,3))
+    pos = randn(3,3)
+    A[pos .< 0] .= false
+    @test all(>=(0), pos[A])
+    @test count(A) == count(>=(0), pos)
+end