diff --git a/CMakeLists.txt b/CMakeLists.txt
index 43a8138c846d60548890f416504215162c6e3b21..acfc2e964a4b4f88a2eab85c5488c8d4ef5e32ad 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -815,7 +815,7 @@ endif ( )
 # OpenMPI 3.0 and higher checks the number of processes against the number of CPUs
 execute_process(COMMAND ${MPIEXEC} --version RESULT_VARIABLE mpi_version_result OUTPUT_VARIABLE mpi_version_output)
 if (mpi_version_result EQUAL 0 AND mpi_version_output MATCHES "\\(Open(RTE| MPI)\\) ([3-9]\\.|1[0-9])")
-   set ( MPIEXEC_PREFLAGS "${MPIEXEC_PREFLAGS} -oversubscribe" )
+   list ( APPEND MPIEXEC_PREFLAGS "-oversubscribe" )
 endif()
 ############################################################################################################################