diff --git a/compareECLFiles.cmake b/compareECLFiles.cmake
index 98dbf68eb..a02e44143 100755
--- a/compareECLFiles.cmake
+++ b/compareECLFiles.cmake
@@ -196,6 +196,48 @@ function(add_test_compare_parallel_restarted_simulation)
                        PROPERTIES RUN_SERIAL 1)
 endfunction()
 
+
+###########################################################################
+# TEST: add_test_split_comm
+###########################################################################
+
+# Input:
+#   - casename: basename (no extension)
+#
+# Details:
+#   - This test class compares the output from a parallel simulation
+#     to that of a parallel simulation running with a custom communicator.
+function(add_test_split_comm)
+  set(oneValueArgs CASENAME FILENAME SIMULATOR ABS_TOL REL_TOL DIR)
+  set(multiValueArgs TEST_ARGS)
+  cmake_parse_arguments(PARAM "$" "${oneValueArgs}" "${multiValueArgs}" ${ARGN} )
+  if(NOT PARAM_DIR)
+    set(PARAM_DIR ${PARAM_CASENAME})
+  endif()
+  set(RESULT_PATH ${BASE_RESULT_PATH}/parallelSplitComm/${PARAM_SIMULATOR}+${PARAM_CASENAME})
+  set(DRIVER_ARGS -i ${OPM_TESTS_ROOT}/${PARAM_DIR}
+                  -r ${RESULT_PATH}
+                  -b ${PROJECT_BINARY_DIR}/bin
+                  -f ${PARAM_FILENAME}
+                  -a ${PARAM_ABS_TOL}
+                  -t ${PARAM_REL_TOL}
+                  -c ${COMPARE_ECL_COMMAND})
+  if(PARAM_MPI_PROCS)
+    list(APPEND DRIVER_ARGS -n ${PARAM_MPI_PROCS})
+  endif()
+
+  opm_add_test(compareParallelSplitComm_${PARAM_SIMULATOR}+${PARAM_FILENAME} NO_COMPILE
+               EXE_NAME ${PARAM_SIMULATOR}
+               DRIVER_ARGS ${DRIVER_ARGS}
+               TEST_ARGS ${PARAM_TEST_ARGS})
+  set_tests_properties(compareParallelSplitComm_${PARAM_SIMULATOR}+${PARAM_FILENAME}
+                       PROPERTIES RUN_SERIAL 1)
+endfunction()
+
+
+###########################################################################
+
+
 if(NOT TARGET test-suite)
   add_custom_target(test-suite)
 endif()
@@ -1188,6 +1230,15 @@ if(MPI_FOUND)
                                                  DIR aquifer-num
                                                  TEST_ARGS --enable-tuning=true --tolerance-cnv=0.00003 --time-step-control=pid --linsolver=cpr)
 
+# Single test to verify that we treat custom communicators correctly.
+  opm_set_test_driver(${PROJECT_SOURCE_DIR}/tests/run-split-comm-test.sh "")
+  add_test_split_comm(CASENAME spe1
+                      FILENAME SPE1CASE2
+                      SIMULATOR flow
+                      ABS_TOL 0.0
+                      REL_TOL 0.0)
+
+
   opm_set_test_driver(${PROJECT_SOURCE_DIR}/tests/run-parallel-regressionTest.sh "")
 
   # Different tolerances for these tests
diff --git a/tests/run-split-comm-test.sh b/tests/run-split-comm-test.sh
new file mode 100755
index 000000000..f3cf738fd
--- /dev/null
+++ b/tests/run-split-comm-test.sh
@@ -0,0 +1,70 @@
+#!/bin/bash
+
+# This runs two parallel cases, one of them with one more process
+# and the --test-split-communicator=true option,
+# then compares the summary and restart files from the two runs.
+# Meant to track regression of the treatment of MPI communicators.
+
+if test $# -eq 0
+then
+  echo -e "Usage:\t$0 <options> -- [additional simulator options]"
+  echo -e "\tMandatory options:"
+  echo -e "\t\t -i <path>     Path to read deck from"
+  echo -e "\t\t -r <path>     Path to store results in"
+  echo -e "\t\t -b <path>     Path to simulator binary"
+  echo -e "\t\t -f <filename> Deck file name"
+  echo -e "\t\t -a <tol>      Absolute tolerance in comparison"
+  echo -e "\t\t -t <tol>      Relative tolerance in comparison"
+  echo -e "\t\t -c <path>     Path to comparison tool"
+  echo -e "\t\t -e <filename> Simulator binary to use"
+  exit 1
+fi
+
+BASE_MPI_PROCS=3
+TEST_MPI_PROCS=4 # should be 1 more than the base
+OPTIND=1
+while getopts "i:r:b:f:a:t:c:e:n:" OPT
+do
+  case "${OPT}" in
+    i) INPUT_DATA_PATH=${OPTARG} ;;
+    r) RESULT_PATH=${OPTARG} ;;
+    b) BINPATH=${OPTARG} ;;
+    f) FILENAME=${OPTARG} ;;
+    a) ABS_TOL=${OPTARG} ;;
+    t) REL_TOL=${OPTARG} ;;
+    c) COMPARE_ECL_COMMAND=${OPTARG} ;;
+    e) EXE_NAME=${OPTARG} ;;
+  esac
+done
+shift $(($OPTIND-1))
+TEST_ARGS="$@"
+
+rm -Rf ${RESULT_PATH}
+mkdir -p ${RESULT_PATH}
+
+echo mpirun -np ${BASE_MPI_PROCS} ${BINPATH}/${EXE_NAME} ${INPUT_DATA_PATH}/${FILENAME}.DATA ${TEST_ARGS} --output-dir=${RESULT_PATH}/base
+mpirun -np ${BASE_MPI_PROCS} ${BINPATH}/${EXE_NAME} ${INPUT_DATA_PATH}/${FILENAME}.DATA ${TEST_ARGS} --output-dir=${RESULT_PATH}/base
+test $? -eq 0 || exit 1
+
+echo mpirun -np ${TEST_MPI_PROCS} ${BINPATH}/${EXE_NAME} --test-split-communicator=true ${INPUT_DATA_PATH}/${FILENAME}.DATA ${TEST_ARGS} --output-dir=${RESULT_PATH}/test
+mpirun -np ${TEST_MPI_PROCS} ${BINPATH}/${EXE_NAME} --test-split-communicator=true ${INPUT_DATA_PATH}/${FILENAME}.DATA ${TEST_ARGS} --output-dir=${RESULT_PATH}/test
+test $? -eq 0 || exit 1
+
+ecode=0
+echo "=== Executing comparison for summary file ==="
+${COMPARE_ECL_COMMAND} -t SMRY -R ${RESULT_PATH}/base/${FILENAME} ${RESULT_PATH}/test/${FILENAME} ${ABS_TOL} ${REL_TOL}
+if [ $? -ne 0 ]
+then
+  ecode=1
+  ${COMPARE_ECL_COMMAND} -t SMRY -a -R ${RESULT_PATH}/base/${FILENAME} ${RESULT_PATH}/test/${FILENAME} ${ABS_TOL} ${REL_TOL}
+fi
+
+echo "=== Executing comparison for restart file ==="
+${COMPARE_ECL_COMMAND} -l -t UNRST ${RESULT_PATH}/base/${FILENAME} ${RESULT_PATH}/test/${FILENAME} ${ABS_TOL} ${REL_TOL}
+if [ $? -ne 0 ]
+then
+  ecode=1
+  ${COMPARE_ECL_COMMAND} -a -l -t UNRST ${RESULT_PATH}/base/${FILENAME} ${RESULT_PATH}/test/${FILENAME} ${ABS_TOL} ${REL_TOL}
+fi
+
+exit $ecode