diff --git a/test/test_distributed.py b/test/test_distributed.py
index 95f220b7e6ad715f933f8e55d2fbd8cd0bcf150d..232c408a07d81ca9b8ea3b7c76b2ed6d8bead96d 100644
--- a/test/test_distributed.py
+++ b/test/test_distributed.py
@@ -32,23 +32,33 @@ import os
 
 # {{{ mpi test infrastructure
 
-def run_test_with_mpi(num_ranks, f, *args):
+def run_test_with_mpi(num_ranks, f, *args, extra_env_vars=None):
     import pytest
     pytest.importorskip("mpi4py")
 
+    if extra_env_vars is None:
+        extra_env_vars = {}
+
     from pickle import dumps
     from base64 import b64encode
 
-    invocation_info = b64encode(dumps((f, args))).decode()
     from subprocess import check_call
 
+    env_vars = {
+            "RUN_WITHIN_MPI": "1",
+            "INVOCATION_INFO": b64encode(dumps((f, args))).decode(),
+            }
+    env_vars.update(extra_env_vars)
+
     # NOTE: CI uses OpenMPI; -x to pass env vars. MPICH uses -env
     check_call([
         "mpiexec", "-np", str(num_ranks),
-        "-x", "RUN_WITHIN_MPI=1",
         "--oversubscribe",
-        "-x", f"INVOCATION_INFO={invocation_info}",
-        sys.executable, "-m", "mpi4py", __file__])
+        ] + [
+            item
+            for env_name, env_val in env_vars.items()
+            for item in ["-x", f"{env_name}={env_val}"]
+        ] + [sys.executable, "-m", "mpi4py", __file__])
 
 
 def run_test_with_mpi_inner():