diff --git a/etc/settings.csh b/etc/settings.csh
index 8159eed539..4fd95a1c9d 100644
--- a/etc/settings.csh
+++ b/etc/settings.csh
@@ -236,11 +236,12 @@ case OPENMPI:
     breaksw
 
 case SYSTEMOPENMPI:
-
-    # This uses the installed openmpi. It needs mpicc installed!
-
+    # use the system installed openmpi, get library directory via mpicc
     set mpi_version=openmpi-system
 
+    # Set to dummy value (but existing directory)
+    setenv MPI_ARCH_PATH /
+
     # Set compilation flags here instead of in wmake/rules/../mplibSYSTEMOPENMPI
     setenv PINC "`mpicc --showme:compile`"
     setenv PLIBS "`mpicc --showme:link`"
diff --git a/etc/settings.sh b/etc/settings.sh
index 5b53c59f2b..9f46523377 100644
--- a/etc/settings.sh
+++ b/etc/settings.sh
@@ -264,6 +264,9 @@ SYSTEMOPENMPI)
     # use the system installed openmpi, get library directory via mpicc
     mpi_version=openmpi-system
 
+    # Set to dummy (but existing directory). Used in Thirdparty Allwmake.
+    export MPI_ARCH_PATH=/
+
     # Set compilation flags here instead of in wmake/rules/../mplibSYSTEMOPENMPI
     export PINC="`mpicc --showme:compile`"
     export PLIBS="`mpicc --showme:link`"