diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 6a79583bc15e9b42512242790058dbfac2838ab6..52c76990a00615307e03da1311741fcc3bbf66f6 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -26,7 +26,7 @@ Pytest POCL:
   script:
   - export PY_EXE=python3
   - export PYOPENCL_TEST=portable:pthread
-  - export EXTRA_INSTALL="pybind11 numpy mako"
+  - export EXTRA_INSTALL="pybind11 numpy mako mpi4py"
   - curl -L -O https://gitlab.tiker.net/inducer/ci-support/raw/main/build-and-test-py-project.sh
   - ". ./build-and-test-py-project.sh"
   tags:
@@ -43,7 +43,7 @@ Pytest Titan V:
   script:
   - py_version=3
   - export PYOPENCL_TEST=nvi:titan
-  - EXTRA_INSTALL="pybind11 numpy mako"
+  - EXTRA_INSTALL="pybind11 numpy mako mpi4py"
   - curl -L -O https://gitlab.tiker.net/inducer/ci-support/raw/main/build-and-test-py-project.sh
   - ". ./build-and-test-py-project.sh"
   tags:
diff --git a/requirements.txt b/requirements.txt
index ff9ca871b7caebcaf92e6fda6c5a4f18b00b1ab2..da6a8fd2183a4f4c3922b0c477bb5030797f3015 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,6 +2,10 @@ numpy
 sympy
 pyrsistent
 pyvkfft
+
+# used in mpi-based tests
+platformdirs
+
 git+https://github.com/inducer/pytools.git#egg=pytools
 git+https://github.com/inducer/pymbolic.git#egg=pymbolic
 git+https://github.com/inducer/islpy.git#egg=islpy