diff --git a/Project.toml b/Project.toml
index 6e651f8f..2e923ad2 100644
--- a/Project.toml
+++ b/Project.toml
@@ -14,6 +14,7 @@ julia = "1.6"
 
 [extras]
 OffsetArrays = "6fe1bfb0-de20-5000-8ca7-80f57d26f881"
+Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 
 [targets]
-test = ["OffsetArrays"]
+test = ["OffsetArrays", "Random"]
diff --git a/src/implementations/SparseArrays.jl b/src/implementations/SparseArrays.jl
index b00bf9d5..19a7d5df 100644
--- a/src/implementations/SparseArrays.jl
+++ b/src/implementations/SparseArrays.jl
@@ -213,6 +213,7 @@ function operate!(
     B::_SparseMat,
     α::Vararg{Union{T,Scaling},N},
 ) where {T,N}
+    rhs_constants = prod(α)
     _dim_check(ret, A, B)
     rowvalA = SparseArrays.rowvals(A)
     nzvalA = SparseArrays.nonzeros(A)
@@ -234,7 +235,7 @@ function operate!(
             ret.colptr[i] = ip0 = ip
             k0 = ip - 1
             for jp in SparseArrays.nzrange(B, i)
-                nzB = nzvalB[jp]
+                nzB = nzvalB[jp] * rhs_constants
                 j = rowvalB[jp]
                 for kp in SparseArrays.nzrange(A, j)
                     k = rowvalA[kp]
diff --git a/test/SparseArrays.jl b/test/SparseArrays.jl
new file mode 100644
index 00000000..17743c74
--- /dev/null
+++ b/test/SparseArrays.jl
@@ -0,0 +1,71 @@
+# Copyright (c) 2019 MutableArithmetics.jl contributors
+#
+# This Source Code Form is subject to the terms of the Mozilla Public License,
+# v.2.0. If a copy of the MPL was not distributed with this file, You can obtain
+# one at http://mozilla.org/MPL/2.0/.
+
+module TestInterfaceSparseArrays
+
+using Test
+
+import MutableArithmetics
+import Random
+import SparseArrays
+
+const MA = MutableArithmetics
+
+function runtests()
+    for name in names(@__MODULE__; all = true)
+        if startswith("$(name)", "test_")
+            @testset "$(name)" begin
+                getfield(@__MODULE__, name)()
+            end
+        end
+    end
+    return
+end
+
+function test_spmatmul()
+    Random.seed!(1234)
+    for m in [1, 2, 3, 5, 11]
+        for n in [1, 2, 3, 5, 11]
+            A = SparseArrays.sprand(Float64, m, n, 0.5)
+            B = SparseArrays.sprand(Float64, n, m, 0.5)
+            ret = SparseArrays.spzeros(Float64, m, m)
+            MA.operate!(MA.add_mul, ret, A, B)
+            @test ret ≈ A * B
+            ret = SparseArrays.spzeros(Float64, m, m)
+            MA.operate!(MA.add_mul, ret, A, A')
+            @test ret ≈ A * A'
+            ret = SparseArrays.spzeros(Float64, m, m)
+            MA.operate!(MA.add_mul, ret, A, B, 2.0)
+            @test ret ≈ A * B * 2.0
+            ret = SparseArrays.spzeros(Float64, m, m)
+            MA.operate!(MA.add_mul, ret, A, B, 2.0, 1.5)
+            @test ret ≈ A * B * 2.0 * 1.5
+        end
+    end
+    return
+end
+
+function test_spmatmul_prefer_sort()
+    Random.seed!(1234)
+    m = n = 100
+    p = 0.01
+    A = SparseArrays.sprand(Float64, m, n, p)
+    B = SparseArrays.sprand(Float64, n, m, p)
+    ret = SparseArrays.spzeros(Float64, m, m)
+    MA.operate!(MA.add_mul, ret, A, B)
+    @test ret ≈ A * B
+    ret = SparseArrays.spzeros(Float64, m, m)
+    MA.operate!(MA.add_mul, ret, A, B, 2.0)
+    @test ret ≈ A * B * 2.0
+    ret = SparseArrays.spzeros(Float64, m, m)
+    MA.operate!(MA.add_mul, ret, A, B, 2.0, 1.5)
+    @test ret ≈ A * B * 2.0 * 1.5
+    return
+end
+
+end  # module
+
+TestInterfaceSparseArrays.runtests()
diff --git a/test/runtests.jl b/test/runtests.jl
index ae1c093c..92d41edc 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -27,6 +27,8 @@ include("matmul.jl")
 include("dispatch.jl")
 include("rewrite.jl")
 
+include("SparseArrays.jl")
+
 # It is easy to introduce macro scoping issues into MutableArithmetics,
 # particularly ones that rely on `MA` or `MutableArithmetics` being present in
 # the current scope. To work around that, include the "hygiene" script in a