diff --git a/base/broadcast.jl b/base/broadcast.jl
index 1896e5edad105..a54016ad00917 100644
--- a/base/broadcast.jl
+++ b/base/broadcast.jl
@@ -1185,7 +1185,7 @@ 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 1fd1b02776b68..bd9cb9e8e8fa3 100644
--- a/test/broadcast.jl
+++ b/test/broadcast.jl
@@ -1116,6 +1116,14 @@ end
     @inferred(test(x, y)) == [0, 0]
 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
+
 # test that `Broadcast` definition is defined as total and eligible for concrete evaluation
 import Base.Broadcast: BroadcastStyle, DefaultArrayStyle
 @test Base.infer_effects(BroadcastStyle, (DefaultArrayStyle{1},DefaultArrayStyle{2},)) |>