diff --git a/.github/workflows/quemb_unittest.yml b/.github/workflows/quemb_unittest.yml
index 2149e413..a6bef97d 100644
--- a/.github/workflows/quemb_unittest.yml
+++ b/.github/workflows/quemb_unittest.yml
@@ -157,8 +157,9 @@ jobs:
     - name: Test with pytest
       run: |
         cd tests
+        export QUEMB_SKIP_EXPENSIVE_TESTS=true
         # QUEMB_SKIP_EXPENSIVE_TESTS=true pytest --doctest-modules --junitxml=junit/quemb-test-results_${{ matrix.python-version }}.xml
-        QUEMB_SKIP_EXPENSIVE_TESTS=true pytest --doctest-modules --junitxml=junit/quemb-test-results_${{ matrix.python-version }}.xml dmrg_molBE_test.py
+        LD_PRELOAD=${{ env.pythonLocation }}/libmkl_core.so pytest -c '--doctest-modules --junitxml=junit/quemb-test-results_${{ matrix.python-version }}.xml dmrg_molBE_test.py'
 
 
     - name: Upload pytest junit results
diff --git a/tests/test_opt_requirements.txt b/tests/test_opt_requirements.txt
index 25e193f5..2f16436c 100644
--- a/tests/test_opt_requirements.txt
+++ b/tests/test_opt_requirements.txt
@@ -1,2 +1,3 @@
+# Optional dependencies for QuEmb's DMRG unit tests.
 block2 --extra-index-url=https://block-hczhai.github.io/block2-preview/pypi/
 git+https://github.com/pyscf/dmrgscf