diff --git a/Project.toml b/Project.toml
index d93698d..8a19c36 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "SparseArraysBase"
 uuid = "0d5efcca-f356-4864-8770-e1ed8d78f208"
 authors = ["ITensor developers <support@itensor.org> and contributors"]
-version = "0.2.8"
+version = "0.2.9"
 
 [deps]
 Accessors = "7d9f7c33-5ae7-4f3b-8dc6-eff91059b697"
diff --git a/src/abstractsparsearrayinterface.jl b/src/abstractsparsearrayinterface.jl
index 6d83385..f8bd0e0 100644
--- a/src/abstractsparsearrayinterface.jl
+++ b/src/abstractsparsearrayinterface.jl
@@ -203,15 +203,25 @@ end
   return SparseArrayDOK{T}(size...)
 end
 
+# map over a specified subset of indices of the inputs.
+function map_indices! end
+
+@interface interface::AbstractArrayInterface function map_indices!(
+  indices, f, a_dest::AbstractArray, as::AbstractArray...
+)
+  for I in indices
+    a_dest[I] = f(map(a -> a[I], as)...)
+  end
+  return a_dest
+end
+
 # Only map the stored values of the inputs.
 function map_stored! end
 
 @interface interface::AbstractArrayInterface function map_stored!(
   f, a_dest::AbstractArray, as::AbstractArray...
 )
-  for I in eachstoredindex(as...)
-    a_dest[I] = f(map(a -> a[I], as)...)
-  end
+  @interface interface map_indices!(eachstoredindex(as...), f, a_dest, as...)
   return a_dest
 end
 
@@ -221,9 +231,7 @@ function map_all! end
 @interface interface::AbstractArrayInterface function map_all!(
   f, a_dest::AbstractArray, as::AbstractArray...
 )
-  for I in eachindex(as...)
-    a_dest[I] = map(f, map(a -> a[I], as)...)
-  end
+  @interface interface map_indices!(eachindex(as...), f, a_dest, as...)
   return a_dest
 end
 
@@ -242,38 +250,32 @@ using ArrayLayouts: ArrayLayouts, zero!
   return @interface interface map_stored!(f, a, a)
 end
 
+# Determines if a function preserves the stored values
+# of the destination sparse array.
+# The current code may be inefficient since it actually
+# accesses an unstored element, which in the case of a
+# sparse array of arrays can allocate an array.
+# Sparse arrays could be expected to define a cheap
+# unstored element allocator, for example
+# `get_prototypical_unstored(a::AbstractArray)`.
+function preserves_unstored(f, a_dest::AbstractArray, as::AbstractArray...)
+  I = first(eachindex(as...))
+  return iszero(f(map(a -> getunstoredindex(a, I), as)...))
+end
+
 @interface interface::AbstractSparseArrayInterface function Base.map!(
   f, a_dest::AbstractArray, as::AbstractArray...
 )
-  # TODO: Define a function `preserves_unstored(a_dest, f, as...)`
-  # to determine if a function preserves the stored values
-  # of the destination sparse array.
-  # The current code may be inefficient since it actually
-  # accesses an unstored element, which in the case of a
-  # sparse array of arrays can allocate an array.
-  # Sparse arrays could be expected to define a cheap
-  # unstored element allocator, for example
-  # `get_prototypical_unstored(a::AbstractArray)`.
-  I = first(eachindex(as...))
-  preserves_unstored = iszero(f(map(a -> getunstoredindex(a, I), as)...))
-  if !preserves_unstored
-    # Doesn't preserve unstored values, loop over all elements.
-    @interface interface map_all!(f, a_dest, as...)
-    return a_dest
+  indices = if !preserves_unstored(f, a_dest, as...)
+    eachindex(a_dest)
+  elseif any(a -> a_dest !== a, as)
+    as = map(a -> Base.unalias(a_dest, a), as)
+    @interface interface zero!(a_dest)
+    eachstoredindex(as...)
+  else
+    eachstoredindex(a_dest)
   end
-  # First zero out the destination.
-  # TODO: Make this more nuanced, skip when possible, for
-  # example if the sparsity of the destination is a subset of
-  # the sparsity of the sources, i.e.:
-  # ```julia
-  # if eachstoredindex(as...) ∉ eachstoredindex(a_dest)
-  #   zero!(a_dest)
-  # end
-  # ```
-  # This is the safest thing to do in general, for example
-  # if the destination is dense but the sources are sparse.
-  @interface interface zero!(a_dest)
-  @interface interface map_stored!(f, a_dest, as...)
+  @interface interface map_indices!(indices, f, a_dest, as...)
   return a_dest
 end
 
@@ -357,9 +359,7 @@ function sparse_mul!(
   β::Number=false;
   (mul!!)=(default_mul!!),
 )
-  # TODO: Change to: `a_dest .*= β`
-  # once https://github.com/ITensor/SparseArraysBase.jl/issues/19 is fixed.
-  storedvalues(a_dest) .*= β
+  a_dest .*= β
   β′ = one(Bool)
   for I1 in eachstoredindex(a1)
     for I2 in eachstoredindex(a2)
diff --git a/test/basics/test_sparsearraydok.jl b/test/basics/test_sparsearraydok.jl
index 642f8c9..08cadf4 100644
--- a/test/basics/test_sparsearraydok.jl
+++ b/test/basics/test_sparsearraydok.jl
@@ -177,4 +177,42 @@ arrayts = (Array,)
     a[1, 2] = 12
     @test sprint(show, "text/plain", a) == "$(summary(a)):\n ⋅  $(eltype(a)(12))\n ⋅    ⋅"
   end
+
+  # Regression test for:
+  # https://github.com/ITensor/SparseArraysBase.jl/issues/19
+  a = SparseArrayDOK{elt}(2, 2)
+  a[1, 1] = 1
+  a .*= 2
+  @test a == [2 0; 0 0]
+  @test storedlength(a) == 1
+
+  # Test aliasing behavior.
+  a = SparseArrayDOK{elt}(2, 2)
+  a[1, 1] = 11
+  a[1, 2] = 12
+  a[2, 2] = 22
+  c1 = @view a[:, 1]
+  r1 = @view a[1, :]
+  r1 .= c1
+  @test c1 == [11, 0]
+  @test storedlength(c1) == 1
+  @test r1 == [11, 0]
+  @test storedlength(r1) == 2
+  @test a == [11 0; 0 22]
+  @test storedlength(a) == 3
+
+  # Test aliasing behavior.
+  a = SparseArrayDOK{elt}(2, 2)
+  a[1, 1] = 11
+  a[1, 2] = 12
+  a[2, 2] = 22
+  c1 = @view a[:, 1]
+  r1 = @view a[1, :]
+  c1 .= r1
+  @test c1 == [11, 12]
+  @test storedlength(c1) == 2
+  @test r1 == [11, 12]
+  @test storedlength(r1) == 2
+  @test a == [11 12; 12 22]
+  @test storedlength(a) == 4
 end