diff --git a/.github/workflows/job4-msmpi.yml b/.github/workflows/job4-msmpi.yml
index 8f8d054ac..06ea65bf0 100644
--- a/.github/workflows/job4-msmpi.yml
+++ b/.github/workflows/job4-msmpi.yml
@@ -58,7 +58,7 @@ jobs:
       - name: Configure
         run: |
           autoreconf -i
-          ./configure --enable-download --prefix="${HOME}/freefem"
+          ./configure CXXFLAGS=-mtune=generic CFLAGS=-mtune=generic FFLAGS=-mtune=generic --enable-generic --enable-download --prefix="${HOME}/freefem"
           ./3rdparty/getall -a -o PETSc
 
       - name: PETSc
diff --git a/.github/workflows/job4-openmpi.yml b/.github/workflows/job4-openmpi.yml
index f501f52d1..1ea66bce1 100644
--- a/.github/workflows/job4-openmpi.yml
+++ b/.github/workflows/job4-openmpi.yml
@@ -56,8 +56,8 @@ jobs:
     runs-on: macos-${{ matrix.version }}
 
     env:
-      CC: gcc
-      CXX: g++
+      CC: clang
+      CXX: clang++
       FC: gfortran
       F77: gfortran
       MPIRUN: /usr/local/bin/mpirun
diff --git a/.github/workflows/job5-msmpi.yml b/.github/workflows/job5-msmpi.yml
index 478cac248..029c768a7 100644
--- a/.github/workflows/job5-msmpi.yml
+++ b/.github/workflows/job5-msmpi.yml
@@ -58,7 +58,7 @@ jobs:
       - name: Configure
         run: |
           autoreconf -i
-          ./configure --enable-download --enable-debug --prefix="${HOME}/freefem"
+          ./configure CXXFLAGS=-mtune=generic CFLAGS=-mtune=generic FFLAGS=-mtune=generic --enable-generic --enable-download --enable-debug --prefix="${HOME}/freefem"
           ./3rdparty/getall -a -o PETSc
 
       - name: PETSc
diff --git a/.github/workflows/job5-openmpi.yml b/.github/workflows/job5-openmpi.yml
index 744a2449b..b9ee93647 100644
--- a/.github/workflows/job5-openmpi.yml
+++ b/.github/workflows/job5-openmpi.yml
@@ -56,8 +56,8 @@ jobs:
     runs-on: macos-${{ matrix.version }}
 
     env:
-      CC: gcc
-      CXX: g++
+      CC: clang
+      CXX: clang++
       FC: gfortran
       F77: gfortran
       MPIRUN: /usr/local/bin/mpirun