diff --git a/.github/workflows/os-blas-test-matrix.yml b/.github/workflows/os-blas-test-matrix.yml
index 0e5fd25fc..f8371e387 100644
--- a/.github/workflows/os-blas-test-matrix.yml
+++ b/.github/workflows/os-blas-test-matrix.yml
@@ -71,8 +71,8 @@ jobs:
             unset | Generic | Apple ) ;; # Found in system
             OpenBLAS )
               brew install openblas
-              echo "BLAS_ROOT=/usr/local/opt/openblas/" >> $GITHUB_ENV
-              echo "LAPACK_ROOT=/usr/local/opt/openblas/" >> $GITHUB_ENV
+              echo "LDFLAGS=-L/opt/homebrew/opt/openblas/lib" >> $GITHUB_ENV
+              echo "CPPFLAGS=-I/opt/homebrew/opt/openblas/include" >> $GITHUB_ENV
               ;;
             *)
               echo "bla_vendor option ${{ matrix.bla_vendor }} not supported"
@@ -204,8 +204,6 @@ jobs:
           path: slycot-src
       - name: Checkout python-control
         uses: actions/checkout@v3
-        with:
-          repository: 'python-control/python-control'
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
diff --git a/control/tests/nyquist_test.py b/control/tests/nyquist_test.py
index af9505354..73a4ed8b6 100644
--- a/control/tests/nyquist_test.py
+++ b/control/tests/nyquist_test.py
@@ -132,18 +132,17 @@ def test_nyquist_basic():
     # Nyquist plot with poles on imaginary axis, omega specified
     # (can miss encirclements due to the imaginary poles at +/- 1j)
     sys = ct.tf([1], [1, 3, 2]) * ct.tf([1], [1, 0, 1])
-    with pytest.warns(UserWarning, match="does not match") as records:
+    with warnings.catch_warnings(record=True) as records:
         count = ct.nyquist_response(sys, np.linspace(1e-3, 1e1, 1000))
-    if len(records) == 0:
-        assert _Z(sys) == count + _P(sys)
-
-    # Nyquist plot with poles on imaginary axis, omega specified, with contour
-    sys = ct.tf([1], [1, 3, 2]) * ct.tf([1], [1, 0, 1])
-    with pytest.warns(UserWarning, match="does not match") as records:
-        count, contour = ct.nyquist_response(
-            sys, np.linspace(1e-3, 1e1, 1000), return_contour=True)
-    if len(records) == 0:
-        assert _Z(sys) == count + _P(sys)
+        if len(records) == 0:
+            # No warnings (it happens) => make sure count is correct
+            assert _Z(sys) == count + _P(sys)
+        elif len(records) == 1:
+            # Expected case: make sure warning is the right one
+            assert issubclass(records[0].category, UserWarning)
+            assert "encirclements does not match" in str(records[0].message)
+        else:
+            pytest.fail("multiple warnings in nyquist_response (?)")
 
     # Nyquist plot with poles on imaginary axis, return contour
     sys = ct.tf([1], [1, 3, 2]) * ct.tf([1], [1, 0, 1])