diff --git a/CMakeLists.txt b/CMakeLists.txt
index 8d6e62282..381f0cd7b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -120,6 +120,11 @@ target_include_directories(pugixml PUBLIC vendor/pugixml/)
 # xtensor header-only library
 #===============================================================================
 
+# CMake 3.13+ will complain about policy CMP0079 unless it is set explicitly
+if (NOT (CMAKE_VERSION VERSION_LESS 3.13))
+  cmake_policy(SET CMP0079 NEW)
+endif()
+
 add_subdirectory(vendor/xtl)
 add_subdirectory(vendor/xtensor)
 target_link_libraries(xtensor INTERFACE xtl)
diff --git a/src/finalize.cpp b/src/finalize.cpp
index 120903f3f..7c39a7c19 100644
--- a/src/finalize.cpp
+++ b/src/finalize.cpp
@@ -127,7 +127,9 @@ int openmc_finalize()
 
   // Free all MPI types
 #ifdef OPENMC_MPI
-  MPI_Type_free(&mpi::bank);
+  int init_called;
+  MPI_Initialized(&init_called);
+  if (init_called) MPI_Type_free(&mpi::bank);
 #endif
 
   return 0;
diff --git a/src/message_passing.cpp b/src/message_passing.cpp
index 278bf924d..aea17f9f4 100644
--- a/src/message_passing.cpp
+++ b/src/message_passing.cpp
@@ -8,8 +8,8 @@ int n_procs {1};
 bool master {true};
 
 #ifdef OPENMC_MPI
-MPI_Comm intracomm;
-MPI_Datatype bank;
+MPI_Comm intracomm {MPI_COMM_NULL};
+MPI_Datatype bank {MPI_DATATYPE_NULL};
 #endif
 
 extern "C" bool openmc_master() { return mpi::master; }
diff --git a/tests/unit_tests/conftest.py b/tests/unit_tests/conftest.py
index aa28be9c3..b69ef0b13 100644
--- a/tests/unit_tests/conftest.py
+++ b/tests/unit_tests/conftest.py
@@ -1,6 +1,17 @@
 import openmc
 import pytest
 
+from tests.regression_tests import config
+
+
+@pytest.fixture(scope='module')
+def mpi_intracomm():
+    if config['mpi']:
+        from mpi4py import MPI
+        return MPI.COMM_WORLD
+    else:
+        return None
+
 
 @pytest.fixture(scope='module')
 def uo2():
diff --git a/tests/unit_tests/test_capi.py b/tests/unit_tests/test_capi.py
index ed0bfd441..c8ad0907c 100644
--- a/tests/unit_tests/test_capi.py
+++ b/tests/unit_tests/test_capi.py
@@ -50,8 +50,8 @@ def pincell_model():
 
 
 @pytest.fixture(scope='module')
-def capi_init(pincell_model):
-    openmc.capi.init()
+def capi_init(pincell_model, mpi_intracomm):
+    openmc.capi.init(intracomm=mpi_intracomm)
     yield
     openmc.capi.finalize()
 
@@ -408,11 +408,11 @@ def test_mesh(capi_init):
     assert msf.mesh == mesh
 
 
-def test_restart(capi_init):
+def test_restart(capi_init, mpi_intracomm):
     # Finalize and re-init to make internal state consistent with XML.
     openmc.capi.hard_reset()
     openmc.capi.finalize()
-    openmc.capi.init()
+    openmc.capi.init(intracomm=mpi_intracomm)
     openmc.capi.simulation_init()
 
     # Run for 7 batches then write a statepoint.
diff --git a/tests/unit_tests/test_complex_cell_capi.py b/tests/unit_tests/test_complex_cell_capi.py
index 365ce4808..a76fa6307 100644
--- a/tests/unit_tests/test_complex_cell_capi.py
+++ b/tests/unit_tests/test_complex_cell_capi.py
@@ -3,7 +3,7 @@ import openmc.capi
 import pytest
 
 @pytest.fixture(autouse=True)
-def complex_cell(run_in_tmpdir):
+def complex_cell(run_in_tmpdir, mpi_intracomm):
 
     openmc.reset_auto_ids()
 
@@ -74,7 +74,7 @@ def complex_cell(run_in_tmpdir):
     model.export_to_xml()
 
     openmc.capi.finalize()
-    openmc.capi.init()
+    openmc.capi.init(intracomm=mpi_intracomm)
 
     yield