diff --git a/.travis.yml b/.travis.yml
index 464ffcb204e0f92368f99be9e1d154cde4edaf3e..0050359c559264de8d6d016b9a2f43ab981fdc95 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -110,6 +110,7 @@ install:
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]] && test -z "$PLUMED_MACPORTS" ; then
       brew update > /dev/null ;
       brew install ccache ;
+      export PLUMED_MPIRUN="mpirun --oversubscribe" ;
     fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get update -qq ; fi
 # install some package - these are fast, we install them anyway