diff --git a/.github/workflows/CI-CPU.yml b/.github/workflows/CI-CPU.yml
index 4efc362..a9848a3 100644
--- a/.github/workflows/CI-CPU.yml
+++ b/.github/workflows/CI-CPU.yml
@@ -31,15 +31,27 @@ jobs:
           - ubuntu-latest
           - macOS-latest
           - windows-latest
+          - macOS-13
         arch:
           - x64
           - x86
+          - aarch64
         env:
           - JULIA_NUM_THREADS: 1
           - JULIA_NUM_THREADS: 2
         exclude:
+          - os: macOS-13
+            arch: x86
+          - os: macOS-13
+            arch: aarch64
           - os: macOS-latest
             arch: x86
+          - os: macOS-latest
+            arch: x64
+          - os: ubuntu-latest
+            arch: aarch64
+          - os: windows-latest
+            arch: aarch64
     steps:
       - uses: actions/checkout@v4
       - uses: julia-actions/setup-julia@v2
@@ -49,6 +61,8 @@ jobs:
       - uses: julia-actions/cache@v2
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
+        env:
+          JULIA_NUM_THREADS: ${{ matrix.env.JULIA_NUM_THREADS }}
   docs:
     name: Documentation
     runs-on: ubuntu-latest
@@ -58,4 +72,4 @@ jobs:
       - uses: julia-actions/julia-docdeploy@latest
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          DOCUMENTER_KEY: ${{ secrets.DOCUMENTER_KEY }}
\ No newline at end of file
+          DOCUMENTER_KEY: ${{ secrets.DOCUMENTER_KEY }}
diff --git a/src/reduce/reduce.jl b/src/reduce/reduce.jl
index 88e535b..06d775b 100644
--- a/src/reduce/reduce.jl
+++ b/src/reduce/reduce.jl
@@ -274,12 +274,12 @@ function _mapreduce_impl(
             if num_tasks <= 1
                 return Base.mapreduce(f, op, src; init=init)
             end
-            return OMT.tmapreduce(
-                f, op, src, init=init,
+            return op(init, OMT.tmapreduce(
+                f, op, src; init=neutral,
                 scheduler=scheduler,
                 outputtype=typeof(init),
                 nchunks=num_tasks,
-            )
+            ))
         else
             # FIXME: waiting on OhMyThreads.jl for n-dimensional reduction
             return Base.mapreduce(f, op, src; init=init, dims=dims)