diff --git a/.github/workflows/post-merge-tests.yml b/.github/workflows/post-merge-tests.yml
index d7b11fdcfb..0fcc0bf7fb 100644
--- a/.github/workflows/post-merge-tests.yml
+++ b/.github/workflows/post-merge-tests.yml
@@ -124,10 +124,12 @@ jobs:
         python3-wheel sundials-devel yaml-cpp-devel hdf5-devel highfive-devel
     - name: Build Cantera
       run: |
-        scons build -j2 debug=n --debug=time \
-        extra_inc_dirs=/usr/include/eigen3 f90_interface=y \
-        libdirname=/usr/lib64 python_package=full system_eigen=y system_fmt=y \
-        system_sundials=y system_yamlcpp=y system_blas_lapack=y hdf_support=y
+        scons build -j2 debug=n --debug=time python_package=full f90_interface=y \
+        extra_inc_dirs=/usr/include/eigen3 libdirname=/usr/lib64 \
+        system_eigen=y system_fmt=y system_blas_lapack=y system_sundials=y \
+        system_yamlcpp=y system_blas_lapack=y hdf_support=y
+      # note: 'system_highfive=y' is omitted as the current packaged version is too old;
+      # once newer version is available in 'latest', this should be tested as well
     - name: Test Cantera
       run:
         scons test verbose_tests=yes --debug=time
@@ -158,20 +160,20 @@ jobs:
     - name: Install Apt dependencies
       run: |
         sudo apt update
-        sudo apt install libboost-dev gfortran libopenmpi-dev libpython3-dev \
+        sudo apt install libboost-dev gfortran libopenmpi-dev \
         libblas-dev liblapack-dev libhdf5-dev libfmt-dev
         gcc --version
     - name: Upgrade pip
       run: python3 -m pip install -U pip setuptools wheel
     - name: Install Python dependencies
       run: |
-        python3 -m pip install ruamel.yaml scons==3.1.2 numpy cython pandas pytest \
+        python3 -m pip install ruamel.yaml scons numpy cython pandas pytest \
         pytest-github-actions-annotate-failures pint
     - name: Build Cantera
       run: |
         python3 `which scons` build env_vars=all -j2 debug=n --debug=time \
         system_fmt=y hdf_libdir=$HDF5_LIBDIR hdf_include=$HDF5_INCLUDEDIR \
-        cc_flags=-D_GLIBCXX_ASSERTIONS
+        system_blas_lapack=y hdf_support=y cc_flags=-D_GLIBCXX_ASSERTIONS
     - name: Test Cantera
       run:
         python3 `which scons` test show_long_tests=yes verbose_tests=yes --debug=time