diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 0eb616c24d..37ab645582 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -56,12 +56,12 @@ jobs:
           rm -rf firedrake_venv
       - name: Build Firedrake
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           cd ..
           # Linting should ignore unquoted shell variable $COMPLEX
           # shellcheck disable=SC2086
           ./firedrake/scripts/firedrake-install \
             $COMPLEX \
-            --honour-petsc-dir \
             --mpicc="$MPICH_DIR"/mpicc \
             --mpicxx="$MPICH_DIR"/mpicxx \
             --mpif90="$MPICH_DIR"/mpif90 \
@@ -87,6 +87,7 @@ jobs:
             || (cat firedrake-install.log && /bin/false)
       - name: Install test dependencies
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           python "$(which firedrake-clean)"
           python -m pip install \
@@ -94,6 +95,7 @@ jobs:
           python -m pip list
       - name: Test Firedrake
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           echo OMP_NUM_THREADS is "$OMP_NUM_THREADS"
           echo OPENBLAS_NUM_THREADS is "$OPENBLAS_NUM_THREADS"
@@ -119,6 +121,7 @@ jobs:
       - name: Test pyadjoint
         if: ${{ matrix.scalar-type == 'real' }}
         run: |
+          unset PETSC_DIR PETSC_ARCH SLEPC_DIR
           . ../firedrake_venv/bin/activate
           cd ../firedrake_venv/src/pyadjoint
           python -m pytest \
diff --git a/scripts/firedrake-install b/scripts/firedrake-install
index 17a8d7fdbc..41bdc21b8f 100755
--- a/scripts/firedrake-install
+++ b/scripts/firedrake-install
@@ -792,6 +792,10 @@ def get_petsc_options(minimal=False):
                 # on macOS with parallel solvers. Its necessity is unclear, so a
                 # review in the future may be required.
                 petsc_options.add("--LDFLAGS=-Wl,-ld_classic,-dead_strip_dylibs")
+            if Version(clt["version"]) >= Version("16"):
+                # Should revisit this flag when the the issue https://gitlab.com/petsc/petsc/-/issues/1692
+                # is resolved.
+                petsc_options.add("--with-cxx-dialect=17")
     elif options.get("with_blas") is not None:
         petsc_options.add("--with-blaslapack-dir={}".format(options["with_blas"]))
         if osname == "Darwin":