diff --git a/.github/workflows/ci-windows.yml b/.github/workflows/ci-windows.yml
index ee6a834..cb1be98 100644
--- a/.github/workflows/ci-windows.yml
+++ b/.github/workflows/ci-windows.yml
@@ -104,4 +104,4 @@
       run: ninja
     - name: Run AVIF Tests
       working-directory: ./build
-      run: ctest -j 2
+      run: ctest -j $Env:NUMBER_OF_PROCESSORS
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c0b3d90..331efaf 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -89,4 +89,4 @@
       run: ninja
     - name: Run AVIF Tests
       working-directory: ./build
-      run: ctest -j 2
+      run: ctest -j $(getconf _NPROCESSORS_ONLN)